How to handle DECREF_INPUTS_AND_REUSE_FLOAT with deferred floats?

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DECREF_INPUTS_AND_REUSE_FLOAT and _Py_DECREF_SPECIALIZED are problematic in that they don't follow standard CPython reference semantics that we plan for the deferred refcounting.

The easiest solution would be to get rid of them. I don't know what's the perf hit from something like that, and whether we can recover it though.