[non-BE] Resolve "USAN: index out of bounds for OMASA JBM decoding to EXT with rate switching"

• Related issues: #1120 (closed)
• Requested reviewers: @tamarapu (as @kiene is on holiday)

Reason why this change is needed

• There is a Clang USAN problem with OMASA JBM decoding to EXT with rate switching. In practice, after a specific combination of switches, metadata output is also wrong.

Description of the change

• This adjusts how the rate switching works when in OMASA external output (including freeing of structures) and also future proofs similar parts in McMASA.

Affected operating points

• Bitstream is BE.
• Non-BE for OMASA EXT output when in rate switching (and probably also needs JBM with time adjustments)
• There should be a minor complexity impact in rate switch due to freeing and reservation happening correctly now