hh: Apply HoGP and DIS serialization behind a flag

Previously this is done only for Floss. Now generalize it for Android
as well. For context, see aosp/3226143.

Bug: 366293212
Bug: 367910199
Test: m -j
Flag: com.android.bluetooth.flags.serialize_hogp_and_dis
Change-Id: I4660f816a320c102eb46d50f47e3c85ccb987fc3