audio policy: concurrent capture

Implement concurrent capture in audio policy manager:
- Attach AudioRecord client to already opened input when possible
instead of systematically opening a new input for each client.
- Always allow inputs to start even in case of concurrency.
- Clients are selectively silenced based on their app state by audio
policy service.
- In case of concurrency on a given input stream, device and source is
chosen based app states and source priority.

Bug: 111438757
Test: Manual capture tests with solotester and Camera, Assistant and Duo
Test: CTS tests for AudioRecord

Change-Id: I302710ff545f67361d9aca89e81de40771ce7fb0