Entropy coder changes and windows_ola changes

[x] Entropy coder and coder_common files converted to fixed
[x] Few updates to window_ola_fx.c, dec_tcx.c, lsp_conv_poly_fx.c
[x] Some modules unit tested, not enabled yet in overall flow.

Testing:
[x] With "ivas-codec-20231128_Update_Ittiam" as reference, 285 are BE with self-test.py.
[x] There are 3 BE failures, the output of whom have maximum loudness difference < 3.
The wave outputs were resampled to 48kHz, channels extracted as mono channels and
tested using MLD tool for loudness difference.