Due to the lack of synchronized connections, the hf_client can not create audio_connection to
hf_ag. Set default number of synchronized connection to 1.
Closes https://github.com/espressif/esp-idf/issues/9537
1. Bugfix for AG audio crash (change the return position)
2. Fix the error macro name and error return in hfp_hf demo
3. Fix the annotation error using UTF-8 ' (from Github)
4. Change or remove the log in SCO related code region.
5. Correct error of introduction of a function.