Properly release accessibility servers

[ge0rdi]

Fixes #2556

[YellowNest]

I had a look. The teardown itself is the right idea, but I think reusing ClearSettingsTreeItemAccessibility() for CHILDID_SELF changes its existing runtime semantics.

That helper is also called during normal tree rebuilds, not only destruction:

• CTreeSettingsDlg::SetGroup() calls SetSettingsTreeAccessibleName() and then ClearSettingsTreeItemAccessibility(). With this change, the latter immediately clears the tree-level name that was just set.
• CSkinSettingsDlg::InitSkinUI() also calls it before rebuilding the tree. Clearing CHILDID_SELF there removes the ANNO_CONTAINER CSettingsTreeAccServer, and I don't see it being re-advised after the rebuild.

So I think item cleanup and final tree teardown should stay separate: keep the existing helper item-only for rebuilds, and clear CHILDID_SELF only from the destroy path. That avoids changing accessibility behavior while the dialog remains alive.

[ge0rdi]

Oki, fair enough.
Lets stick with your PR.
Thank you very much for helping with this.