gd: Pair 2 phones

Allow GD Pixel3 phones to pair with legacy Pixel2.
Dependent on a few other minor patches too large to be
written in the margin.

Bug: 141555841
Test: Paired GD Pixel 3 to legacy Pixel2
Test: bluetooth_test_gd

Change-Id: I76be337ac2b4041dd679b0caa169156af2f43eed