Reset sys.argv after running child script/module

[joerick]

Fixes #241.

Using trace as an example of a script that changes sys.argv:

Before:

$ python -m pyinstrument -m trace --trace wikipedia_article_word_count.py
...
  _     ._   __/__   _ _  _  _ _/_   Recorded: 17:06:48  Samples:  476
 /_//_/// /_\ / //_// / //_'/ //     Duration: 0.819     CPU time: 0.437
/   _/                      v4.5.1

Program: trace

0.818 <module>  trace.py:1
...

After:

$ python -m pyinstrument -m trace --trace wikipedia_article_word_count.py
...
  _     ._   __/__   _ _  _  _ _/_   Recorded: 17:08:07  Samples:  482
 /_//_/// /_\ / //_// / //_'/ //     Duration: 0.821     CPU time: 0.444
/   _/                      v4.5.1

Program: /Users/joerick/Projects/pyinstrument/pyinstrument/__main__.py -m trace --trace wikipedia_article_word_count.py

0.821 <module>  trace.py:1
...

aside: Note this doesn't change pyinstrument's way of passing sys.argv to children. The behaviour is that all of

• python script.py arg1 arg2
• python -m script.py arg1 arg2
• pyinstrument script.py arg1 arg2

and

• python -m module arg1 arg2
• python -m pyinstrument -m module arg1 arg2
• pyinstrument -m module arg1 arg2

look the same from the child's perspective. That's verified in the test

pyinstrument/test/test_cmdline.py

Line 81 in af87938

def test_script_execution_details(self, pyinstrument_invocation, tmp_path: Path):

.

That test was faulty as written, I've also fixed that in this PR.

[matthiasdiener]

Thanks @joerick, this looks good!