Added fuzzers for libbt-audio-hal-interface

This patch adds following fuzz targets:
libbt_audio_hal_a2dp_encoding_fuzzer,
libbt_audio_hal_le_audio_software_fuzzer,
libbt_audio_hal_hearing_aid_software_encoding_fuzzer
and libbt_audio_hal_client_interface_fuzzer.

Test: ./libbt_audio_hal_a2dp_encoding_fuzzer
Test: ./libbt_audio_hal_le_audio_software_fuzzer
Test: ./libbt_audio_hal_hearing_aid_software_encoding_fuzzer
Test: ./libbt_audio_hal_client_interface_fuzzer
Bug: 189053432

Change-Id: I2e8a986c568e348036ea71e83ea246fdbeba9529