Sanitize profile filename

[SkafteNicki]

What does this PR do?

Fixes #21365
Make sure that filenames are sanitized when profiler is trying to dump .prof files.
This will currently crash if there are characters such as "/" in the filename, which happens if the user has a ModelCheckpoint with a monitoring metric like "val/acc".

Before submitting

• Was this discussed/agreed via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you list all the breaking changes introduced by this pull request?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

PR review

Anyone in the community is welcome to review the PR.
Before you start reviewing, make sure you have read the review guidelines. In short, see the following bullet-list:

Reviewer checklist

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

---

📚 Documentation preview 📚: https://pytorch-lightning--21395.org.readthedocs.build/en/21395/

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 79%. Comparing base (79ffe50) to head (ab7d8fb).
✅ All tests successful. No failed tests found.

❗ There is a different number of reports uploaded between BASE (79ffe50) and HEAD (ab7d8fb). Click for more details.

HEAD has 1195 uploads less than BASE

Flag	BASE (79ffe50)	HEAD (ab7d8fb)
cpu	299	30
lightning_fabric	75	0
pytest	150	0
python3.12	89	9
python3.12.7	90	9
lightning	150	15
python3.11	60	6
python3.10	30	3
python	30	3
pytorch2.1	30	6
pytest-full	149	30
pytorch_lightning	74	15
pytorch2.6	15	3
pytorch2.4.1	15	3
pytorch2.3	15	3
pytorch2.2.2	15	3
pytorch2.5.1	15	3
pytorch2.9	15	3
pytorch2.7	15	3
pytorch2.8	14	3

Additional details and impacted files

@@            Coverage Diff            @@
##           master   #21395     +/-   ##
=========================================
- Coverage      87%      79%     -8%     
=========================================
  Files         269      266      -3     
  Lines       23804    23757     -47     
=========================================
- Hits        20626    18732   -1894     
- Misses       3178     5025   +1847