Jitter leftovers

This is a follow-up to !581 (comment 15932) about potential improvements to the Jitter - JBM contribution under VARIABLE_SPEED_DECODING and JBM_TSM_ON_TCS

Tagging @bayers.

• There is a number of formal imperfections in the code.
• The following functions are not currently covered by the Coverage test. Could some more JBM conditions be added, please?

• pcmdsp_fifo_write_zero()
• ivas_sba_prototype_renderer_sf()
• ivas_binaural_cldfb_sf()

• Finally, the usage_dec() is not very clear to me.

#ifdef VARIABLE_SPEED_DECODING
    fprintf( stdout, "-VS fac             : Varaible Speed mode: change speed of playout fac as integer in percent. fac<100 faster, fac>100 slower\n" );
#endif
#ifdef JBM_TSM_ON_TCS
#ifdef DEBUG_JBM_CMD_OPTION
    fprintf( stdout, "-VOIP_framesize     : VoIP mode: acoustic frontend fetch frame size (must be multiples of 5!)\n" );
#endif

#endif
    fprintf( stdout, "                      The decoder may read rtpdump files containing TS26.445 Annex A.2.2\n" );
    fprintf( stdout, "                      EVS RTP Payload Format. The SDP parameter hf_only is required.\n" );
    fprintf( stdout, "                      Reading RFC4867 AMR/AMR-WB RTP payload format is not supported.\n" );

Do the last three printout lines correspond to "-VS fac" option or something else, please?

• Is there any limitation for "fac" values and does the framework accept whatever value?
• And just for completeness, the EVS JBM is not affected I guess. So the "-VS fac" option is valid for IVAS modes only, right?
• Is the comment /* :TODO: also provide CLDFB output FIFO if things work out */ still valid?
• Is the comment /*:TODO: wrap this maybe nicer without directly accessing the st_ivas struct...*/ still valid?
• Is the comment /* TODO: JBM use renderer residual samples here */ still valid?
• Is the comment /* TODO(mcjbm): ringbuffer capacity should be configurable by user */ still valid?