SBA order in the bitstream

Currently, the SBA order stored in hEncoderConfig->sba_planar is sent in the bitstream at all SBA bitrates. However, it currently represents the coded SBA order and not the input audio SBA order.

As a follow up to the preliminary discussions, I propose that

1. SBA order in the bitstream should contain the input audio SBA order
2. In case of coding at lower bitrates where HOA coding is not supported, a printout message should be printed out, e.g.

HOA coding is not supported below 256 kbps, switching to FOA.

3. Consequently, a new parameter, e.g. hEncoderConfig->sba_planar_input will need to be introduced and used for bitstream coding.
4. Probably the original parameter hEncoderConfig->sba_planar should be moved to st_ivas->sba_planar and handled similarly as e.g. nchan_transport or sba_mode. (?)

Please share your comments and views.