Port MR2123 from float - 20250513 cleanup

Basic Info

• Original merge request in float repo: ivas-codec-pc/ivas-codec!2123 (merged)

Acceptance of

• #define UNIFIED_DECODING_PATHS_LEFTOVERS /* VA: issue 880: remove leftovers after NONBE_UNIFIED_DECODING_PATHS */
• #define NONBE_1300_TDREND_LARGE_ITD /* Eri: issue 1300: There was a bug feeding 1.25 ms frames to the TD renderer, causing out-of-buffer access. This was resolved. However, it is still possible that modeled HRTF with large ITDs could trigger out-of-buffer access. This adds a check to prevent this.*/
• #define NONBE_1293_SR_HRTF /* VA: issue 1293: add support of external HRTFs in split rendering */ -> ported as part of the HRTF update ⚠️ already cleaned out with !2178 (merged) / 2180

Note: thick box indicates whether the switch was already ported