Huge static RAM consumption when HRTFs are loaded from file

When HRTFs for binaural rendering are loaded from a file, the static RAM consumption is huge compared to the consumption when HRTFs are loaded from ROM tables. The main reason is that handles for all four binaural renderers are always allocated and loaded while only one (or two in case of OMASA/OSBA) is really needed.

This issue was already discussed in !1717 (comment 49931).

A solution would be to move the HRTFs loading from the initialization to the frame decoding loop. After feeding the received bitstream to the decoder, the following steps would need to be performed:

1. an IVAS format and signaling is read; in the attached branch it is the function IVAS_DEC_ReadFormat()
2. HRTFs are loaded and appropriate handles allocated/deallocated; this is done in the first frame and potentially in the bitrate switching; in the attached branch it is the function IVAS_DEC_LoadHrtfFromFile()
3. Continue as usual by calling IVAS_DEC_Setup() and IVAS_DEC_GetTcSamples()

The following table summarizes the static RAM impact at some operating points involving all renderers [bytes]:

condition	binaural renderer	HRTFs from ROM	HRTFs from file	HRTFs from file FIX
SBA @64 kbps to BINAURAL	Parametric Binaural Renderer	466,892	1,777,192	466,920
SBA @128 kbps to BINAURAL	FastConv Binaural Renderer	914,082	2,213,470	2,196,510 939,710
ISM2 @64kbps to BINAURAL	Time Domain Object Renderer	372,028	1,694,520	369,028
ISM2 @64kbps to BINAURAL_ROOM_IR	Crend Binaural Renderer	951,868	2,278,248	951,916

Note: SBA @128 kbps HRTFs from file FIX number corresponds to loading of all HRTFs (FOA/HOA2/HOA3/reverb). When only the really used one is loaded, the number goes down to 939,710 bytes.

A possible solution is shown in the attached branch under FIX_HRTF_LOAD switch. Note that, for the moment, only the non-JBM path has been implemented and non-combined formats have been verified.