Adds snippets for Audio page

[kul3r4]

Adds snippets for https://developer.android.com/training/wearables/apps/audio.
All code was accurate except for the method setSuppressPlaybackWhenUnsuitableOutput which has been renamed to setSuppressPlaybackOnUnsuitableOutput, hence not compiling.

[snippet-bot]

Here is the summary of changes.

You are about to add 6 region tags.

• wear/src/main/java/com/example/wear/snippets/audio/AudioActivity.kt:33, tag android_wear_audio_detect_devices
• wear/src/main/java/com/example/wear/snippets/audio/AudioActivity.kt:48, tag android_wear_exoplayer_audio_output_suppression
• wear/src/main/java/com/example/wear/snippets/audio/AudioActivity.kt:54, tag android_wear_exoplayer_audio_output_suppression_listener
• wear/src/main/java/com/example/wear/snippets/audio/AudioActivity.kt:63, tag android_wear_audio_detect_devices_sample
• wear/src/main/java/com/example/wear/snippets/audio/AudioActivity.kt:76, tag android_wear_audio_register_callback
• wear/src/main/java/com/example/wear/snippets/audio/BluetoothSettings.kt:24, tag android_wear_bluetooth_settings

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