AutoCompleteBox don't lose text selection when contextmenu opens

[punker76]

What does the pull request do?

When implementing copy and paste context menu items for AutoCompleteBox it's not possible because text selection gets lost.

This issue was solved also for TextBox in #4498

What is the current behavior?

Selection is gone.

What is the updated/expected behavior with this PR?

Selection should be the same.

How was the solution implemented (if it's not obvious)?

Checklist

• [x] Added unit tests (if possible)?
• [ ] Added XML documentation to any related classes?
• [x] Consider submitting a PR to https://github.com/AvaloniaUI/avalonia-docs with user documentation

Breaking changes

Obsoletions / Deprecations

Fixed issues

Fixes #17453

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0053177-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[cla-avalonia]

• [x] All contributors have signed the CLA.

[punker76]

@cla-avalonia agree

[avaloniaui-bot]

You can test this PR using the following package version. 11.3.999-cibuild0053187-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]