Allow pairing over unseen transport

BTM_SecBond locally rejected pairing over a transport which was not seen
to be supported by the remote device.
Priviledged applications can select the transport to used for pairing.
Some priviledged applications may choose to pair without performing the
device discovery or without performing device discovery long enough for
the BT stack to see the target device over the selected transport.

Test: mmm packages/modules/Bluetooth
Flag: com.android.bluetooth.flags.pairing_on_unknown_transport
Bug: 334805274
Bug: 335239971
Change-Id: Ifc71295668a6af1e003b41818ffd1f23c6b553c9