ivas_front_vad_spar() functions/sub funcs, stereo mdct stereo enc funcs

[x] Converted/Integrated the following functions and its sub functions in ivas_front_vad_spar():
noise_est_down(), correlation_shift(), dtx(), find_wsp(), StableHighPitchDetect(), multi_harm(), vad_param_updt(), ivas_smc_gmm(), ivas_long_enr()
[x] In stereo mdct stereo encoder module, following functions are ported to fixed point:
RCcontextMapping_encode2_estimate_bandWise, RCcontextMapping_encode2_estimate_bandWise_start, RCcontextMapping_encode2_estimate_no_mem_s17_LCS, find_last_nz_pair, IGFEncStereoEncoder, IGF_MsStereoDecision, calcCoh, FindSplitRatio, GetChannelEnergyRatio, MsStereoDecision, QuantSpecEstimateBits, SQ_gain_estimate_stereo, context_update, convertToBwMS, convertToMS, dft_ana_init, initMdctItdHandling, initMdctStereoEncData, ms_inv_mask_processing, ms_processing, stereo_coder_tcx, stereo_mdct_enc_destroy, write_itd_data, write_stereo_to_bitstream, tcx_scalar_quantization

EVS 26.444 BE test passes.
decoder pytests:
MLD scores:
Original inputs: 562 failed, 374 skipped
MLD > 10: 46
MLD > 5 : 108
MLD < 5 : 408
+10dB inputs: 562 failed, 374 skipped
MLD > 10: 168
MLD > 5 : 185
MLD < 5 : 209
-10dB inputs: 562 failed, 374 skipped
MLD > 10: 13
MLD > 5 : 47
MLD < 5 : 502

encoder pytests results:
MLD scores:
Original inputs: 562 tests: 90 passes, 472 failures, 374 skipped
MLD > 10: 16
MLD > 5 : 31
MLD < 5 : 515
+10dB inputs: 562 tests: 90 passes, 472 failures, 374 skipped
MLD > 10: 26
MLD > 5 : 92
MLD < 5 : 444
-10dB inputs: 562 tests: 76 passes, 486 failures, 374 skipped
MLD > 10: 5
MLD > 5 : 19
MLD < 5 : 538