Bluetooth: HFP_HF: Use HF object to replace conn object

Use HF object to replace conn object for callbacks `disconnected`,
`sco_connected`, `service`, `outgoing`, `remote_ringing`, `incoming`,
`incoming_held`, `accept`, `reject`, `terminate`, `call_held`,
`signal`, `roam`, `battery`, `ring_indication`, `dialing`, `clip`,
`vgm`, `vgs`, `inband_ring`, `operator`, `codec_negotiate`, and
`ecnr_turn_off`.

Use HF object to replace conn object for functions `bt_hfp_hf_cli`,
`bt_hfp_hf_vgm`, `bt_hfp_hf_vgs`, `bt_hfp_hf_get_operator`,
`bt_hfp_hf_accept`, `bt_hfp_hf_reject`, `bt_hfp_hf_terminate`,
`bt_hfp_hf_hold_incoming`, `bt_hfp_hf_query_respond_hold_status`,
`bt_hfp_hf_number_call`, `bt_hfp_hf_memory_dial`, `bt_hfp_hf_redial`,
`bt_hfp_hf_audio_connect`, `bt_hfp_hf_select_codec`,
`bt_hfp_hf_set_codecs`, and `bt_hfp_hf_turn_off_ecnr`.

Add a parameter `struct bt_hfp_hf *hf` to callback `connected`.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>