[SPARK-3399][PySpark] Test for PySpark should ignore HADOOP_CONF_DIR and YARN_CONF_DIR

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2270 from sarutak/SPARK-3399 and squashes the following commits:

7613be6 [Kousuke Saruta] Modified pyspark script to ignore environment variables YARN_CONF_DIR and HADOOP_CONF_DIR while testing
SPARK-3211 .take() is OOM-prone with empty partitions

Instead of jumping straight from 1 partition to all partitions, do exponential
growth and double the number of partitions to attempt each time instead.

Fix proposed by Paul Nepywoda

Author: Andrew Ash <andrew@andrewash.com>

Closes #2117 from ash211/SPARK-3211 and squashes the following commits:

8b2299a [Andrew Ash] Quadruple instead of double for a minor speedup
e5f7e4d [Andrew Ash] Update comment to better reflect what we're doing
09a27f7 [Andrew Ash] Update PySpark to be less OOM-prone as well
3a156b8 [Andrew Ash] SPARK-3211 .take() is OOM-prone with empty partitions
[Build] suppress curl/wget progress bars

In the Jenkins console output, `curl` gives us mountains of `#` symbols as it tries to show its download progress.

![noise from curl in Jenkins output](http://i.imgur.com/P2E7yUw.png)

I don't think this is useful so I've changed things to suppress these progress bars. If there is actually some use to this, feel free to reject this proposal.

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #2279 from nchammas/trim-test-output and squashes the following commits:

14a720c [Nicholas Chammas] suppress curl/wget progress bars
[SPARK-3361] Expand PEP 8 checks to include EC2 script and Python examples

This PR resolves [SPARK-3361](https://issues.apache.org/jira/browse/SPARK-3361) by expanding the PEP 8 checks to cover the remaining Python code base:
* The EC2 script
* All Python / PySpark examples

Author: Nicholas Chammas <nicholas.chammas@gmail.com>

Closes #2297 from nchammas/pep8-rulez and squashes the following commits:

1e5ac9a [Nicholas Chammas] PEP 8 fixes to Python examples
c3dbeff [Nicholas Chammas] PEP 8 fixes to EC2 script
65ef6e8 [Nicholas Chammas] expand PEP 8 checks
[SPARK-3409][SQL] Avoid pulling in Exchange operator itself in Exchange's closures.

This is a tiny teeny optimization to move the if check of sortBasedShuffledOn to outside the closures so the closures don't need to pull in the entire Exchange operator object.

Author: Reynold Xin <rxin@apache.org>

Closes #2282 from rxin/SPARK-3409 and squashes the following commits:

1de3f88 [Reynold Xin] [SPARK-3409][SQL] Avoid pulling in Exchange operator itself in Exchange's closures.
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