gh-100227: Only Use deepfreeze for the Main Interpreter (gh-103794)

gh-100227: Only Use deepfreeze for the Main Interpreter (gh-103794)

Deep-frozen code objects are cannot be shared (currently) by
interpreters, due to how adaptive specialization can modify the
bytecodes. We work around this by only using the deep-frozen objects in
the main interpreter. This does incur a performance penalty for
subinterpreters, which we may be able to resolve later.