Sapphire 14 24 ss 1013 deep freeze and deep merge

@tony-spataro-rs added HashTools.deep_freeze! and .deep_merge
the latter differs from deep_merge! because it clones before merging

Ah, good point; deep_clone2 is part of the interface contract. I'll add some @deprecated and @todo notes, and perhaps someday we can clean up the interface when we bump right_support to v3.