Optimize maintenance family of methods

[bitfaster]

Try applying aggressive optimization to the maintenance methods. This is a tiny bit better for LFU, appears to be noise for LRU.

This would likely need to be removed if building on NET7 or NET8, because it can cancel PGO.

[coveralls]

coverage: 99.141% (+0.02%) from 99.121%
when pulling e6b0e05 on users/alexpeck/agglfu
into 5f0a8b8 on main.

[bitfaster]

Superseded by #530