Merge changes I0e74fc26,Ibb0e21c0,I7756a9a9,I74bd0138,I5c1a648c, ...

* changes:
  Remove module_start_up_callbacked_wrapper
  Flatten BTM_DeviceReset (and address a todo from 2014)
  Flatten bta_sys_hw_api_enable
  flatten send_bta_sys_hw_event(BTA_SYS_API_ENABLE_EVT)
  Pull BTA_SYS_API_ENABLE_EVT out of bta_dm_enable
  Flatten BTA_EnableBluetooth
  Pull BTA_EnableBluetooth out of btif_init_ok
  No need to post btif_init_ok
  Pull out bta_ar_init from bta_sys_init
  appl_trace_level is already set to the right value
  Flatten BTE_InitStack
  Flatten btu_init_core
  btu_task_start_up -> main_thread_start_up