[SPARK-3772] Allow `ipython` to be used by Pyspark workers; IPython support improvements:

This pull request addresses a few issues related to PySpark's IPython support:

- Fix the remaining uses of the '-u' flag, which IPython doesn't support (see SPARK-3772).
- Change PYSPARK_PYTHON_OPTS to PYSPARK_DRIVER_PYTHON_OPTS, so that the old name is reserved in case we ever want to allow the worker Python options to be customized (this variable was introduced in #2554 and hasn't landed in a release yet, so this doesn't break any compatibility).
- Introduce a PYSPARK_DRIVER_PYTHON option that allows the driver to use `ipython` while the workers use a different Python version.
- Attempt to use Python 2.7 by default if PYSPARK_PYTHON is not specified.
- Retain the old semantics for IPYTHON=1 and IPYTHON_OPTS (to avoid breaking existing example programs).

There are more details in a block comment in `bin/pyspark`.

Author: Josh Rosen <joshrosen@apache.org>

Closes #2651 from JoshRosen/SPARK-3772 and squashes the following commits:

7b8eb86 [Josh Rosen] More changes to PySpark python executable configuration:
c4f5778 [Josh Rosen] [SPARK-3772] Allow ipython to be used by Pyspark workers; IPython fixes:
[SPARK-3798][SQL] Store the output of a generator in a val

This prevents it from changing during serialization, leading to corrupted results.

Author: Michael Armbrust <michael@databricks.com>

Closes #2656 from marmbrus/generateBug and squashes the following commits:

efa32eb [Michael Armbrust] Store the output of a generator in a val. This prevents it from changing during serialization.
SPARK-3811 [CORE] More robust / standard Utils.deleteRecursively, Utils.createTempDir

I noticed a few issues with how temp directories are created and deleted:

*Minor*

* Guava's `Files.createTempDir()` plus `File.deleteOnExit()` is used in many tests to make a temp dir, but `Utils.createTempDir()` seems to be the standard Spark mechanism
* Call to `File.deleteOnExit()` could be pushed into `Utils.createTempDir()` as well, along with this replacement
* _I messed up the message in an exception in `Utils` in SPARK-3794; fixed here_

*Bit Less Minor*

* `Utils.deleteRecursively()` fails immediately if any `IOException` occurs, instead of trying to delete any remaining files and subdirectories. I've observed this leave temp dirs around. I suggest changing it to continue in the face of an exception and throw one of the possibly several exceptions that occur at the end.
* `Utils.createTempDir()` will add a JVM shutdown hook every time the method is called. Even if the subdir is the parent of another parent dir, since this check is inside the hook. However `Utils` manages a set of all dirs to delete on shutdown already, called `shutdownDeletePaths`. A single hook can be registered to delete all of these on exit. This is how Tachyon temp paths are cleaned up in `TachyonBlockManager`.

I noticed a few other things that might be changed but wanted to ask first:

* Shouldn't the set of dirs to delete be `File`, not just `String` paths?
* `Utils` manages the set of `TachyonFile` that have been registered for deletion, but the shutdown hook is managed in `TachyonBlockManager`. Should this logic not live together, and not in `Utils`? it's more specific to Tachyon, and looks a slight bit odd to import in such a generic place.

Author: Sean Owen <sowen@cloudera.com>

Closes #2670 from srowen/SPARK-3811 and squashes the following commits:

071ae60 [Sean Owen] Update per @vanzin's review
da0146d [Sean Owen] Make Utils.deleteRecursively try to delete all paths even when an exception occurs; use one shutdown hook instead of one per method call to delete temp dirs
3a0faa4 [Sean Owen] Standardize on Utils.createTempDir instead of Files.createTempDir
[SPARK-3654][SQL] Unifies SQL and HiveQL parsers

This PR is a follow up of #2590, and tries to introduce a top level SQL parser entry point for all SQL dialects supported by Spark SQL.

A top level parser `SparkSQLParser` is introduced to handle the syntaxes that all SQL dialects should recognize (e.g. `CACHE TABLE`, `UNCACHE TABLE` and `SET`, etc.). For all the syntaxes this parser doesn't recognize directly, it fallbacks to a specified function that tries to parse arbitrary input to a `LogicalPlan`. This function is typically another parser combinator like `SqlParser`. DDL syntaxes introduced in #2475 can be moved to here.

The `ExtendedHiveQlParser` now only handle Hive specific extensions.

Also took the chance to refactor/reformat `SqlParser` for better readability.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #2698 from liancheng/gen-sql-parser and squashes the following commits:

ceada76 [Cheng Lian] Minor styling fixes
9738934 [Cheng Lian] Minor refactoring, removes optional trailing ";" in the parser
bb2ab12 [Cheng Lian] SET property value can be empty string
ce8860b [Cheng Lian] Passes test suites
e86968e [Cheng Lian] Removes debugging code
8bcace5 [Cheng Lian] Replaces digit.+ to rep1(digit) (Scala style checking doesn't like it)
d15d54f [Cheng Lian] Unifies SQL and HiveQL parsers
[SPARK-3824][SQL] Sets in-memory table default storage level to MEMORY_AND_DISK

Using `MEMORY_AND_DISK` as default storage level for in-memory table caching. Due to the in-memory columnar representation, recomputing an in-memory cached table partitions can be very expensive.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #2686 from liancheng/spark-3824 and squashes the following commits:

35d2ed0 [Cheng Lian] Removes extra space
1ab7967 [Cheng Lian] Reduces test data size to fit DiskStore.getBytes()
ba565f0 [Cheng Lian] Maks CachedBatch serializable
07f0204 [Cheng Lian] Sets in-memory table default storage level to MEMORY_AND_DISK
[SPARK-3834][SQL] Backticks not correctly handled in subquery aliases

The queries like SELECT a.key FROM (SELECT key FROM src) \`a\` does not work as backticks in subquery aliases are not handled properly. This PR fixes that.

Author : ravipesala ravindra.pesalahuawei.com

Author: ravipesala <ravindra.pesala@huawei.com>

Closes #2737 from ravipesala/SPARK-3834 and squashes the following commits:

0e0ab98 [ravipesala] Fixing issue in backtick handling for subquery aliases
[SPARK-2805] Upgrade Akka to 2.3.4

This is a second rev of the Akka upgrade (earlier merged, but reverted). I made a slight modification which is that I also upgrade Hive to deal with a compatibility issue related to the protocol buffers library.

Author: Anand Avati <avati@redhat.com>
Author: Patrick Wendell <pwendell@gmail.com>

Closes #2752 from pwendell/akka-upgrade and squashes the following commits:

4c7ca3f [Patrick Wendell] Upgrading to new hive->protobuf version
57a2315 [Anand Avati] SPARK-1812: streaming - remove tests which depend on akka.actor.IO
2a551d3 [Anand Avati] SPARK-1812: core - upgrade to akka 2.3.4
[SPARK-3889] Attempt to avoid SIGBUS by not mmapping files in ConnectionManager

In general, individual shuffle blocks are frequently small, so mmapping them often creates a lot of waste. It may not be bad to mmap the larger ones, but it is pretty inconvenient to get configuration into ManagedBuffer, and besides it is unlikely to help all that much.

Author: Aaron Davidson <aaron@databricks.com>

Closes #2742 from aarondav/mmap and squashes the following commits:

a152065 [Aaron Davidson] Add other pathway back
52b6cd2 [Aaron Davidson] [SPARK-3889] Attempt to avoid SIGBUS by not mmapping files in ConnectionManager
Merge remote-tracking branch 'upstream/master' into dtrunner-update
bug fix for SPARK-3934