Remove duplicated code: TBE

The core-coder duplicates several TBE-related functions. This issue is to track the removal of duplications in functions such as:

• wb_tbe_enc_ivas_fx() vs. wb_tbe_enc_fx()
• ivas_wb_tbe_dec_fx() vs wb_tbe_dec_fx()
• fb_tbe_enc_ivas_fx() vs fb_tbe_enc_fx()
• fb_tbe_dec_ivas_fx() vs fb_tbe_dec_fx()
• InitSWBencBuffer_ivas_fx() vs InitSWBencBuffer_fx()
• etc.