Check which of our mobile prefs and configuration changes are still valid for GeckoView

There are some prefs and configuration options left after Firefox for Android got essentially cut out of the tree. We should go over things we set and clean up unneeded changes for GeckoView.

• webchannel.allowObject.urlWhitelist
  • Move to 001-base-profile.js (I don't understand why we'd want it only for Android)
• privacy.clearOnShutdown.*
  • Still okay, not sure why we want this for Android
• media.realtime_decoder.enabled
  • Still okay
• dom.w3c_touch_events.enabled
  • The pref exists, not sure it can even be really overridden for Android...
• dom.w3c_pointer_events.multiprocess.android.enabled
  • Remove! Changed in ca799a4a and in 48c01f0a.
• media.hls.enabled
  • Still valid, check the original issue (#29859 (closed)), and the issue about re-enabling the feature (#30139).
• intl.locale.requested
  • Remove: used in all platforms now
• security.webauth.webauthn_enable_android_fido2
  • Still needed, we still haven't switched to a free alternative
• extensions.torbutton.launch_warning