Switch to idmap2

Switch from idmap to idmap2.

This CL is the safety pin for idmap2. If idmap2 causes issues during
dogfooding it is easy go back to idmap by reverting this CL.

Once idmap2 has proven itself during a suitable period of time, the
FEATURE_FLAG_IDMAP2 flag and the obsolete idmap code will be removed.

Also add an .rc file to tell init to launch idmap2d.

Bug: 78815803
Test: atest OverlayDeviceTests OverlayHostTests
Change-Id: I5ca1388ac2f8a9379fed0c257247d351a5c7a3c4