PandoraServer: Rename android.proto to os.proto

Rename android.proto to os.proto to be more
specific accross the different OS implementing
the bt-test-interfaces.
This interface is gathering every OS specific action
such as logging and permissions.

Test: atest pts-bot
Bug: 291995194
Change-Id: I5d44b4e511f00a7c827ba3d6d5f920138f030760