Release settings accessibility servers before DLL unload

[YellowNest]

Summary

Release the MSAA dynamic-annotation servers owned by the settings trees before their hosting DLL can be unloaded.

Root cause

The accessibility work from Open-Shell#2518 registers CSettingsTreeAccServer instances through IAccPropServices::SetHwndPropServer.

Those registrations can outlive the settings dialog unless they are explicitly cleared. After Open-Shell exits, StartMenuDLL may be unloaded while oleacc still retains marshaled references to those servers. A later accessibility annotation can trigger CPropMgrImpl::Clean, which then attempts to call CSettingsTreeAccServer::Release() through the stale vtable address in the unloaded module.

That matches the crash in Open-Shell#2556.

Changes

• add a full settings-tree accessibility cleanup helper
• clear all per-item state/name/role annotations before item handles disappear
• clear the tree-level container annotation and accessible name
• run cleanup from both settings-tree destroy paths while child HWNDs are still valid
• keep the existing partial item cleanup used when trees are rebuilt during normal dialog use

Validation

Static review completed against current upstream master. Build and runtime validation pending.

[ge0rdi]

I have created Open-Shell#2557 PR in the meantime.
I think it does the same as yours, just a bit simpler.

Can you have a look?