CTA2075: Finalize the loudness configurator API

Remove @hide annotation for the public API surface

Return boolean for add/removeMediaCodec which allows the client
to track the state of the successfully registered audio codecs

Fixed edge case when a unconfigured MediaCodec is added to the loudness
configurator.

Test: adb shell device_config put media_audio android.media.audio.loudness_configurator_api true
Test: atest LoudnessCodecConfiguratorTest
Bug: 298463873
Bug: 299652613
Change-Id: I0c3479e9bcd1558305655858250b3fb447483987