RCA Perf: Reduce RuntimeFeatureFlags size

[Stefan J. Wernli (swernli)]

This change removes QubitAllocation and MustBeInlined feature flags in favor of tracking those via out-of-band hash sets. QubitAllocation was only ever used to determine callables whose entire call chain must be inlined, while MustBeInlined was about tracking call expressions that must be inlined. By tracking these separately, the RuntimeFeatureFlags enum can be reduced back to u32 and significantly improve RCA perf.

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[Stefan J. Wernli (swernli)]

Going to close this for now. The complexity trade-off relative to the perf gain makes this not a high priority at the moment. Will return to this idea if/when we need to squeeze any other performance out of the RCA stage.