AudioService: update getPreferredDevicesForStrategy

Use the cache stored in AudioDeviceInventory instead of
querying the AudioPolicyManager.
This avoids reflecting the preferred device due to setCommunicationDevice.

Bug: 417481226
Flag: com.android.media.audio.update_preferred_devices_for_strategy
Test: atest AudioManagerTest#testPreferredDevicesForStrategy
Test: atest NonDefaultDeviceForStrategyTest

Change-Id: I704c7c618e5ce306240c1292268d5bfcadba2bd2