Proposed updates to IVAS float code

This is a merge request which contains a proposed update of the IVAS floating point code for Ittiam to consider in their IVAS BASOP conversion. The code comes from https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/releases/20231128_Update_Ittiam and has been merged with the current main to resolve the conflicts present in main.

The code is not bit-exact with respect to the previous IVAS float code update https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/releases/20231012_Update_Ittiam, but it has been verified manually to give bit-exact result with the source release using self_test.py on the 288 testable conditions (since the -fec DEBUGGING feature is removed from the prepared code, the FEC tests are not run).