BassClientStateMachine: Add support for Long Writes

According to BASS 1.0v specification Write Long Characteristic Value
GATT Sub-Procedure is mandatory if the Add Source operation is
supported.

Tag: #feature
Bug: 300217671
Test: atest BassClientStateMachineTest
Change-Id: Id499819159a4eb26842cef3a7e6b48335529c875