Floss: Refactor hfp phone state function

1. Move as many duplicated code (such as phone_state_change
/ start_sco_call_impl / simple_at_response) into the
xxxx_impl functions.

2. Early return if not in MPS mode, we have not yet support
those function in production.

3. Seperate uhid_send_input_report into
uhid_send_hook_switch_input_report and
uhid_send_phone_mute_input_report to make it more
clear on the propose when using it.

4. streamline usage of phone_ops_enabled and mps_qualification_enabled
  * HfpCallbacks -> Only allowed in telephony or mps mode
  * DBus command -> Only allowed in mps mode
  * UHID output -> -> Only allowed in telephony mode

Bug: 336763584
Test: Conduct the following manual tests
  pair Bluetooth Headset
  Google Meet: headset is able hang-up the call
Test: Conduct the following manual tests
  pair Bluetooth Headset
  login Ring Central and place an incoming-call
  answer the call by headset
  hangup the call by headset
Test: Conduct the following manual tests
  pair Bluetooth Headset
  login Ring Central and place an incoming-call
  answer the call on Ring Central
  hangup the call from headset
Test: atest bluetooth_test_gd
Tag: #floss
Flag: EXEMPT, no behavior change on Android; Floss-only changes
Change-Id: I655db3bf5055ab34d5506365278c2a3068b5f822