[AdvancedPaste] Custom Actions follow-up fixes #1

[drawbyperpetual]

Summary of the Pull Request

Fixes the following issues with this PR:

• Removes a workaround to enable and disable custom actions when Advanced Paste window is shown. Note that the issue addressed by the workaround (that the custom actions list-view is sometimes not properly grayed out visually when disabled) is not addressed.
• Fixes an issue where using an in-app shortcut - ctrl+ - results in multiple preview items on the flyout.
• Fixes an issue where using a keyboard shortcut for a disabled custom action still brings up the Advanced Paste window.

PR Checklist

• Closes: #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

• Tested fixes
• Sanity check of Advanced Paste