Add seekNext and seekPrev commandbuttons to the Android 12 "Compact" notification by default

[tzugen]

Currently the "compact" notification in Android 12 using the DefaultMediaNotificationProvider shows only the Play/Pause button.

Our users frequently requested it contains the seek buttons as well, so we added them by assigning a COMMAND_KEY_COMPACT_VIEW_INDEX to them.

I would propose that the seek buttons get this flag by default as it seems to be most common that the basic buttons of a media player are prev, play/pause, and next.

For reference our custom class:

class CustomNotificationProvider(ctx: Context) :
    DefaultMediaNotificationProvider(ctx),
    KoinComponent {

    // By default the skip buttons are not shown in compact view. 
    // We add the COMMAND_KEY_COMPACT_VIEW_INDEX to show them
    override fun getMediaButtons(
        session: MediaSession,
        playerCommands: Player.Commands,
        customLayout: ImmutableList<CommandButton>,
        playWhenReady: Boolean
    ): ImmutableList<CommandButton> {
        val commands = super.getMediaButtons(session, playerCommands, customLayout, playWhenReady)

        commands.forEachIndexed { index, command ->
            command.extras.putInt(COMMAND_KEY_COMPACT_VIEW_INDEX, index)
        }

        return commands
    }
}

[tonihei]

@tianyif Could you take a look and see if this is something we want to enable by default?

[tianyif]

I'm making a change to address this, which should be available in main branch next week.