Expose an Output Switcher dialog for system routing

The new dialog will hide app and playback related metadata and will
only control system routing.

Test: adb shell am broadcast -a com.android.systemui.action.LAUNCH_SYSTEM_MEDIA_OUTPUT_DIALOG com.android.systemui
Bug: 284227163
Flag: NA
Change-Id: I13bbcfe9c5446e41f722a154b7740d2c472afad4