Use existing function to call photon mosaic

[lauraporta]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?
Working on tests I spotted a few improvements I could do in the tests and I've made a separate PR.

What does this PR do?

• Moved the run_photon_mosaic helper function from tests/test_unit/test_metadata.py to tests/conftest.py, allowing all tests to import and use it instead of duplicating code.
• Updated integration tests in tests/test_integration/test_whole_workflow.py to use the centralized run_photon_mosaic helper instead of manually constructing subprocess calls.
• Removed the unused map_of_tiffs fixture from tests/conftest.py to reduce clutter and confusion.

How has this PR been tested?

Local test run

Is this a breaking change?

No

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit

[lauraporta]

@alessandrofelder, PR is ready for review 🙂

[alessandrofelder]

Tried to quickfix the windows CI failure by enforcing use of bash, but we should check whether we really need pwd 🤔 (if that is indeed the issue)

[alessandrofelder]

Hopefully after including fixes from #77 CI will now pass, and we can merge 🤞

[alessandrofelder]

Thanks @lauraporta - I am happy with this now 🎉