Public API enum names

This is a follow-up of #521 (closed) and !905 (closed): public API enums should have a name starting with the prefix IVAS_ to reduce the risk of clashing symbols. The same applies to the enum members.

In particular, this comprises:

• rename AUDIO_CONFIG to IVAS_AUDIO_CONFIG
• rename HEAD_ORIENT_TRK_T to IVAS_HEAD_ORIENT_TRK_T
• rename MASA_DECODER_EXT_OUT_META_HANDLE to IVAS_MASA_DECODER_EXT_OUT_META_HANDLE

Similarly, the public constants should start with IVAS_, e.g.

• rename QC_ABS_COEFF to IVAS_ROOM_ABS_COEFF

Next,

• add notes to highlight cases when public and internal constants are the same