[Common] NotificationUtil helper class with FileWatcher

[davidegiacometti]

Summary of the Pull Request

Replace the current WarnIfElevationIsRequired inline function with a proper helper class that uses FileWatcher.
The new helper allows to cache the option and uses the FileWatcher to listen for changes in the general settings JSON.
It will prevent AOT and FZ to constantly read the general settings JSON.

Note that WarnIfElevationIsRequired is also used by the Workspaces snapshot tool but only once.

PR Checklist

• Closes: Always On Top - Reading its config file (settings.json) way too often #36586
• 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 manually:

• General > Show a warning for functionality issues when running alongside elevated applications > Off
  • Verified that AOT, FZ and Workspaces snapshot tool don't show the notification
• General > Show a warning for functionality issues when running alongside elevated applications > On
  • Verified that AOT, FZ and Workspaces snapshot tool show the notification
  • Verified that AOT and FZ don't show the notification a second time
• Verified that AOT and FZ read the general settings JSON when the option is changed
• Verified using Process Monitor that AOT and FZ don't constantly read the general settings JSON

[davidegiacometti]

/azp run

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