DO NOT MERGE: CtsVerifier: Respect Window Manager volume keys config

Re-implement aosp/625111 since its removal. For devices that set
config_handleVolumeKeysInWindowManager, a change like this will always
be required in USBAudioPeripheralButtonsActivity, otherwise there will
be an unhandled assumption in the test.

Bug: 67777923
Test: Vega
Change-Id: I432cd63dca5e0c9ebbaca1b8cb34bd9471be7103