IO-771: Add test exposing getFullPathNoEndSeparator OS inconsistency

[Reranko05]

This PR adds a unit test reproducing IO-771.

FilenameUtils.getFullPathNoEndSeparator behaves inconsistently on
Windows vs POSIX systems when resolving directory paths.

This PR intentionally adds a failing test only; I’m happy to follow up
with an implementation once the expected cross-platform behavior is agreed upon.

[Reranko05]

This test exposes IO-771, but expected cross-platform behavior is unclear.
Converting to draft to avoid blocking CI.
Happy to update the test or add a fix once the desired behavior is agreed.

[garydgregory]

Hello @Reranko05
This test mixes testing 2 APIs in a confusing manner.
Instead, use the newly added FilenameUtilsTest.testGetFullPathNoEndSeparator_IO_771() and base you fix on that.
Thank you.

[garydgregory]

So you're not going to update this PR with a fix?

[Reranko05]

Apologies for the confusion, I closed this PR to avoid blocking CI after realizing the test already existed upstream.
I’ve now submitted a separate PR with the actual fix, based on FilenameUtilsTest.testGetFullPathNoEndSeparator_IO_771, as you suggested.
Happy to continue the discussion there.

FIX PR : #824