Add owners to coretests quicksettings dir

Adds OWNERS file to
core/tests/coretests/src/android/service/quicksettings, to cover the
directory. Other directories have an OWNERS file already. Reusing owners
file from existing quicksettings dir.

Test: Changing OWNERS file
Bug: 295006271
Change-Id: Ia278116b661b8cbdc2f2f7810889ea27a3772592