MLD improvements for SBA-PLC and MultiChannel cases

• EVS 26.444 BE test passes.
• decoder pytests:
  MLD scores:
  Original inputs: 562 failed, 374 skipped
  MLD > 10: 9
  MLD > 5 : 14
  MLD < 5 : 539
  +10dB inputs: 562 failed, 374 skipped
  MLD > 10: 28
  MLD > 5 : 88
  MLD < 5 : 446
  -10dB inputs: 562 failed, 374 skipped
  MLD > 10: 1
  MLD > 5 : 13
  MLD < 5 : 548
• 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