Create a new topshim API for the BTIF hfp client (btif_hf_client).

Bug: 262045500
Test: mma -j $(nproc)
Test: ./build.py
Test: system/gd/cert/run --clean --topshim
Tag: #floss
Change-Id: I978aba3d5b0124c7562ab9b0ff6310b3f350e92b