Fix for ltv crashes and changes for mld improvements

[x] Add fix for ltv crash [ltv-stereo at 32 kbps, 48kHz in, 48kHz out, DTX on, random FER at 5%, bandwidth switching] with 10dB scaled input. Updated scale in fd_cng_decfx.c
[x] High MLD Fix - [stv-Multi-channel 5_1 at 24.4 kbps, 48kHz in, 48kHz out, STEREO out]
[x] Fix for 10dB_neg input ltv crash: Test case - ltv-stereo at 32 kbps, 48kHz in, 32kHz out, random FER at 5%
[x] Removed saturation for synthFB buffer
[x] Improved precision for few buffers in MC path

• EVS 26.444 BE test passes.
• decoder pytests:
  MLD scores:
  Original inputs: 562 failed, 374 skipped
  MLD > 10: 2
  MLD > 5 : 26
  MLD < 5 : 534
  +10dB inputs: 562 failed, 374 skipped
  MLD > 10: 44
  MLD > 5 : 139
  MLD < 5 : 379
  -10dB inputs: 562 failed, 374 skipped
  MLD > 10: 0
  MLD > 5 : 6
  MLD < 5 : 556
• encoder pytests results:
  MLD scores:
  Original inputs: 562 tests:
  MLD > 10: 18
  MLD > 5 : 67
  MLD < 5 : 477
  +10dB inputs: 562 tests:
  MLD > 10: 69
  MLD > 5 : 122
  MLD < 5 : 371
  -10dB inputs: 562 tests:
  MLD > 10: 5
  MLD > 5 : 24
  MLD < 5 : 533