MediaRouter: Update proguard configs
MediaRouter: Update proguard configs

Remove obsolete -keep rule for MediaRouteActionProvider.
* aapt2 started generating -keep rules for "actionProviderClass" since
  sept 2019: https://cs.android.com/android/platform/superproject/+/master:frameworks/base/tools/aapt2/java/ProguardRules.cpp;drc=dc5de7b23b53205b18f7c9dec6c7882c499cf835;l=164

Add an -assumevalues for DEBUG fields.

Bug: 127531139
Change-Id: If09d6e1d5d403b9ab67360c0571713e8611448c6
AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx