Fix #59935: pillar_roots.write on pillar subdirs

[niflostancu]

What does this PR do?

Fixes the pillar_roots.write's call to salt.utils.verify.clean_path to account for subdirectory writes.

What issues does this PR fix or reference?

Fixes: #59935

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltstack.com/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

No

[Ch3LL]

This will require a changelog and would you please add a test similar to this: aafc5ed#diff-e3e8844bfd715f8094e0c7e1d4294e6d638132fd46e14786ff2ab948e7b48511R34 but testing with a subdir. For example: sub/../root_dir/.

[Ch3LL]

@niflostancu bump, did you see my change requests?

[niflostancu]

Oh god, sorry, I completely forgot about this (I've been busy with other projects) :(
I will fix them tomorrow ;)

[niflostancu]

Hello, I added the supplementary testcase (testing for subdir/../../ that traverses outside the pillar root) + changelog.

My fix simply calls clean_path with subdir=True argument for the pillar_roots to be able to write inside a subdirectory.
I see that it has its own unit tests (tests/unit/utils/test_verify.py) which can be further augmented with path traversal checks (which would benefit any modules using it).