Move UUID grabbing logic from bta_dm_disc_result to bta_dm_gatt_disc_complete

Also, clean up bta_dm_disc_result.

Bug: 330675788
Bug: 335732980
Flag: com.android.bluetooth.flags.separate_service_and_device_discovery
Test: mma -j32
Change-Id: I8ba07bd8d44b793dc7b13fc98692cc83c54308be