Refactor testing of wheels

[JCGoran]

• add pytest-based tests to script
• refactor to also work outside of top-level dir
• use temp dirs everywhere to not pollute current dir

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.40%. Comparing base (bc913ef) to head (d96d8e9). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1174 +/- ## ======================================= Coverage 88.40% 88.40% ======================================= Files 175 175 Lines 12934 12934 ======================================= Hits 11434 11434 Misses 1500 1500 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.40%. Comparing base (bc913ef) to head (0104e15). Report is 3 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1174 +/- ## ======================================= Coverage 88.40% 88.40% ======================================= Files 175 175 Lines 12934 12934 ======================================= Hits 11434 11434 Misses 1500 1500 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[bbpbuildbot]

Logfiles from GitLab pipeline #196118 (:white_check_mark:) have been uploaded here!

Status and direct links:

• :white_check_mark: test:intel
• :white_check_mark: spack_setup
• :white_check_mark: build:intel
• :white_check_mark: build:nvhpc
• :white_check_mark: test:nvhpc