Another way to handle multiple Inputs cache policies

[desertaxle]

These changes handle multiple Inputs cache policies by combining them in a __post_init__ method on CompoundCachePolicy and avoiding nesting compound policies when adding or subtracting.

Note this update will change how cache keys are computed in some cases.

[codspeed-hq]

CodSpeed Performance Report

Merging #16786 will not alter performance

_{Comparing redundant-inputs-another-way (dccd63f) with redundant-inputs (7fdbd4b)}

Summary

✅ 2 untouched benchmarks

[zzstoatzz]

aha nice - much cleaner