[Pandora] Implementing advertising interfaces

Based on discussion in aosp/2193570, moving to this CL because of merge
conflicts + lazy.

Tag: #feature
Bug: 245578454
Test: Test: GAP PTS tests in future CLs
Ignore-AOSP-First: Cherry-pick from AOSP
Merged-In: I3ac8a0e2d735148ec5628e230149544cb25c2e8f
Change-Id: I3ac8a0e2d735148ec5628e230149544cb25c2e8f