Combine getInputForAttr perm checks

Push all permission checks to a single function, which is called in
the middle of the APM function after the mix (and virtualdeviceid) is
selected.

This ensures that we don't incorrectly check perms for default vdi.

To enable this, add a method in the AudioPolicyClient which
evaluates perms for a particular input request to keep the perm checks
out of APM.

Test: CtsMediaAudioTestCases
Bug: 374870131
Fixes: 343523722
Flag: EXEMPT infeasible bugfix
Change-Id: I0f83d26fb7ad3b08a5a89d3ee58701315a91ae6d