base

Add hidden API to prepare for increasing calendar support

This adds hidden APIs for supporting settng allowed availabilities and
attendee types, adding the tentative availability and resource
attendee type, color indexes for calendars and events, and a colors
table.

b/5317399 b/5309787 b/5207781 b/5347210

Change-Id: I8dec4d0ebb0523b34bd420a0ab62bf5d0650996f