[SPARK-3271] delete unused methods in Utils

delete no used method in Utils

Author: scwf <wangfei1@huawei.com>

Closes #2160 from scwf/delete-no-use-method and squashes the following commits:

d8f6b0d [scwf] delete no use method in Utils
SPARK-3265 Allow using custom ipython executable with pyspark

Although you can make pyspark use ipython with `IPYTHON=1`, and also change the python executable with `PYSPARK_PYTHON=...`, you can't use both at the same time because it hardcodes the default ipython script.

This makes it use the `PYSPARK_PYTHON` variable if present and fall back to default python, similarly to how the default python executable is handled.

So you can use a custom ipython like so:
`PYSPARK_PYTHON=./anaconda/bin/ipython IPYTHON_OPTS="notebook" pyspark`

Author: Rob O'Dwyer <odwyerrob@gmail.com>

Closes #2167 from robbles/patch-1 and squashes the following commits:

d98e8a9 [Rob O'Dwyer] Allow using custom ipython executable with pyspark
[HOTFIX] Wait for EOF only for the PySpark shell

In `SparkSubmitDriverBootstrapper`, we wait for the parent process to send us an `EOF` before finishing the application. This is applicable for the PySpark shell because we terminate the application the same way. However if we run a python application, for instance, the JVM actually never exits unless it receives a manual EOF from the user. This is causing a few tests to timeout.

We only need to do this for the PySpark shell because Spark submit runs as a python subprocess only in this case. Thus, the normal Spark shell doesn't need to go through this case even though it is also a REPL.

Thanks davies for reporting this.

Author: Andrew Or <andrewor14@gmail.com>

Closes #2170 from andrewor14/bootstrap-hotfix and squashes the following commits:

42963f5 [Andrew Or] Do not wait for EOF unless this is the pyspark shell
[HOTFIX][SQL] Remove cleaning of UDFs

It is not safe to run the closure cleaner on slaves.  #2153 introduced this which broke all UDF execution on slaves.  Will re-add cleaning of UDF closures in a follow-up PR.

Author: Michael Armbrust <michael@databricks.com>

Closes #2174 from marmbrus/fixUdfs and squashes the following commits:

55406de [Michael Armbrust] [HOTFIX] Remove cleaning of UDFs
[SQL] Fixed 2 comment typos in SQLConf

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

Closes #2172 from liancheng/sqlconf-typo and squashes the following commits:

115cc71 [Cheng Lian] Fixed 2 comment typos in SQLConf
[SPARK-3230][SQL] Fix udfs that return structs

We need to convert the case classes into Rows.

Author: Michael Armbrust <michael@databricks.com>

Closes #2133 from marmbrus/structUdfs and squashes the following commits:

189722f [Michael Armbrust] Merge remote-tracking branch 'origin/master' into structUdfs
8e29b1c [Michael Armbrust] Use existing function
d8d0b76 [Michael Armbrust] Fix udfs that return structs