Match ee spec for ee extensions in TestFileFinder

We need to match ee spec for ee extensions in TestFileFinder when foss_test_only: false

Given `foss_test_only: false`
  and ee extension file: `ee/app/models/ee/user.rb`
  then test files should include:
     - spec/models/user_spec.rb
     - ee/spec/models/ee/user_spec.rb 
     - ee/spec/models/user_spec.rb