test_runner: add cwd option to run

[pmarchini]

I'm opening this PR as a draft to have a place where we can discuss this implementation.

Some background context:

During #54225, we discussed the possibility of adding a new option to run.
This new option would be cwd.

This change could impact many other parts of the code, such as:
#54225 (comment)

I just pushed a new commit.

Nice. I realized that this new cwd option may introduce new bugs in at least three places:

• With --experimental-test-isolation=none.
• With code coverage reporting.
• With test locations.

For this reason, we decided to work on this in a separate PR (#54225 (comment)).