Precision improvements and bug fixes for encoder

[x] Bug fix in core_signal_analysis_high_bitrate_ivas_fx

[x] [Bug-fix] minor logic correction in stereo_td_get_td_itd_fx

[x] Precision improvement inside wb_vad_ivas_fx for the selection of snr_outlier_index

[x] Minor bug fix in stereo_mdct_core_enc_fx

[x] Fixes in unclr_classifier