Navigation telemetry for 'Clear All NuGet Storage' Command in VS Settings

[donnie-msft]

Bug

Fixes: NuGet/Home#13968

Description

Instrument the navigated telemetry event for the 'Clear All NuGet Storage' command in the Visual Studio settings.
Since the event is standardized and already doesn't include PII, no assessment was done to attach another event.

• A property tracks whether the settings are existing legacy VS Settings, or Unified Settings which will be implemented later. For now, this is always false.
• Testing the functionality of the new helper method to create the event.

Example of the event after pressing "Clear All NuGet Storage":

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.