Pixel perfect group detail

- Remove extra GroupDetailTheme and just use the
ContactDetailActivityTheme

- Remove split style action bar on group detail page,
Fix pressed state sizes for "group source" button

- Remove intent filter on group list activity
that was added temporarily during development to
allow launching the group list without the main
PeopleActivity (when the split of the Contacts app
into People/Phone were still under construction)
https://android-git.corp.google.com/g/#/c/109558/5/AndroidManifest.xml

Bug: 4686433

Change-Id: I6f9aa0c94f520e90489ad63aaad07501156c6539