feat(auto): equalizer folder in the browse tree, one toggle on playback

On-device feedback: two identical icons on the car's now-playing screen,
one of which looked dead. It worked -- but head units render custom
actions icon-first, so cycling six presets behind one static glyph was
invisible.

A monochrome icon cannot encode which of six presets is active. Android
Auto separates the idioms deliberately: custom actions for stateless
toggles, browsable lists for choosing among options.

- Playback screen keeps one action: equalizer on/off, state-aware icons
- New Ecualizador folder lists Desactivar plus the six presets by name,
  active one marked
- The preset-cycling action and its drawable are removed

Supersedes the redesign's no-equalizer-folder rule, which predated
knowing custom actions do not surface state in a car.

# Conflicts:
#	lib/l10n/app_ar.arb
#	lib/l10n/app_bn.arb
#	lib/l10n/app_de.arb
#	lib/l10n/app_en.arb
#	lib/l10n/app_es.arb
#	lib/l10n/app_fr.arb
#	lib/l10n/app_hi.arb
#	lib/l10n/app_id.arb
#	lib/l10n/app_it.arb
#	lib/l10n/app_ja.arb
#	lib/l10n/app_pt.arb
#	lib/l10n/app_ru.arb
#	lib/l10n/app_zh.arb

android/app/src/main/res/drawable/ic_auto_eq_off.xml

@@ -0,0 +1,3 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android" android:width="24dp" android:height="24dp" android:viewportWidth="24" android:viewportHeight="24">
+  <path android:fillColor="#FFFFFF" android:pathData="M3,5L21,5L21,7L3,7Z M14,3L17,3L17,9L14,9Z M3,11L21,11L21,13L3,13Z M7,9L10,9L10,15L7,15Z M3,17L21,17L21,19L3,19Z M17,15L20,15L20,21L17,21Z M2,20L4,22L22,4L20,2Z" />
+</vector>

android/app/src/main/res/drawable/ic_auto_eq_on.xml

@@ -0,0 +1,3 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android" android:width="24dp" android:height="24dp" android:viewportWidth="24" android:viewportHeight="24">
+  <path android:fillColor="#FFFFFF" android:pathData="M3,5L21,5L21,7L3,7Z M14,3L17,3L17,9L14,9Z M3,11L21,11L21,13L3,13Z M7,9L10,9L10,15L7,15Z M3,17L21,17L21,19L3,19Z M17,15L20,15L20,21L17,21Z" />
+</vector>