change md sync delay in ext renderer to integer type

• Related issues: #1420, also this BASOP MR: sa4/audio/ivas-basop!2466 (merged)
• Requested reviewers: @tamarapu, @sagnowski, @pihlajakuja

Reason why this change is needed

• Simplifies code and (my hope) makes one spot of the BASOP implementation in sa4/audio/ivas-basop!2411 easier to handle.

Description of the change

• MD sync delay argument is changed from float to int16_t.

Affected operating points

• Nothing, should be BE except for veeeery high delay values (anything above 2**16) in ext renderer.