tests/FileGlobs.py: Dynamically generate files and directory for gitignore tests

Directories like `file_globs_ci_testfiles`, `bears_ci_testfiles` and the files inside them can be dynamically generated during running the tests and removed afterward.

Not sure if it's a good idea as this won't make much difference size-wise but it'll definitely reduce some files in the repository.

status/needs discussion

Start with tests/FileGlobs.py and the gitignore test fixtures named in the issue, including file_globs_ci_testfiles and bears_ci_testfiles. Check how these files and directories are currently used during test runs, then determine whether they can be generated before tests and removed afterward. Done means the tests still pass without keeping those fixtures in the repository.

Written by the indexing model from the issue text.