Add hints to update sync scope when a test file is out of scope

[mnoah1]

This change adds additional guidance when users have synced their test cases, but have then navigated to a file that is outside of their Bazel sync scope. Instead of a lack of test run arrows with no clear reason why, they will now see a greyed out run arrow with further information.

• Open a file that's outside of the current scope.
• Logic from Resolve based on open files #24 attempts to expand this file's target and add its test cases to the test explorer.
• With this PR, if the step above fails, decorators will now be added in the gutter to help provide further guidance, at the locations where the run arrows would normally appear.
  • 
• Adjust Project Scope will open the .bazelproject file for editing, and sync now triggers the test explorer's existing sync functionality.
• This functionality is behind the bazelbsp.autoExpandTarget setting as it is part of that logic.