Merge changes I7eb89883,I93295962,I3ffe28ef,Ice072495,Iba166d9a, ...

Merge changes I7eb89883,I93295962,I3ffe28ef,Ice072495,Iba166d9a, ...

* changes:
  Simplify stack/l2cap/l2c_utils::l2cu_create_conn_br_edr
  Simplify stack/l2cap/l2c_link::l2c_link_role_changed
  Remove poor placement for SCN from tACL_CB
  add stack/btm/btm_scn
  Add tBTM_CB::btm_scn[BTM_MAX_SCN_]
  Simplify stack/l2cap/l2c_utils::l2cu_adj_id
  Precisely name tL2C_CB::tL2C_LCB::id
  Remove tL2C_CB::tL2C_LCB::info_rx_bits
  Encapsulate tL2C_CB::tL2C_LCB::link_flush_tout_
  Precisely name tL2C_CB::num_used_lcbs
  Encapsulate tL2C_CB::tL2C_LCB::disc_reason
  Remove set-once-never-execute l2cb.is_flush_active