Add ArcSettings and SettingsGoogle to the legacy allowlist

Settings-core is already in the allowlist, ArcSettings and
SettingsGoogle need to compile the same source files but were
in Android.mk files.  Add them to the allowlist so they can
be converted to Android.bp.

Bug: 175124789
Test: m RunSettingsGoogleRoboTests RunArcSettingsRoboTests
Change-Id: I73bef76ecc517223827ac6f3cb1f0624c738fb9d