The root of the issue, as identified by Jake-Faulkner in his PR
(!120099), was that after changes in commit 195bb4f8f5,
`BKE_libblock_ensure_unique_name` would not always correctly set
`bmain->is_memfile_undo_written` to false when an ID name was actually
modified.
However, after analyzing a bit more the code in ID renaming, it appeared
that `BKE_libblock_ensure_unique_name` was not needed and only made
things more confusing. Some ID renaming code (from RNA, the Outliner,
and some do_version areas) would then do some manual ID renaming
operations and then call it, instead of simply using the existing 'all
in one' `BKE_libblock_rename` function.
This commit removes `BKE_libblock_ensure_unique_name` and all of its
usages, and simplify all code previously using it by calling
`BKE_libblock_rename` instead.
NOTE: The only non-trivial (not-so-nice) aspect of this commit is the
changes needed in the Outliner renaming code, since here the name of the
ID is directly edited, before calling the rename function, so this edit
needs to be undone to allow calling the generic ID rename API.
Pull Request: https://projects.blender.org/blender/blender/pulls/120196
cb66cc3028