[BASOP-CI] Add Segmental SNR computation to pytest tests

• Related issues: sa4/audio/ivas-basop#785 (closed)
• Requested reviewers: @norvell

Reason why this change is needed

• Add SSNR measure for verifying the fixed-point codec

Description of the change

• Add SSNR computation option to testsystem

Affected operating points

• None, CI change only
• Will not affect float repo CI