AIDL Effect: Update locking in EffectImpl

Avoid locking for all EffectContext calls.
Locking inside context seems not necessary for now as all binder calls
already serialized.
Add BassBoost AIDL placeholder implementation.

Bug: 261646550
Test: atest VtsHalAudioEffectTargetTest

Change-Id: Iaa41f013d5756801553e20b995aab5ddc845cf32