We generally do not use a for loop for worklist iteration since one runs into
weird issues around always needing to recompute the worklist size since it may
change per iteration. In contrast, using the while loop approach that just pops
off the back avoids such implicit weirdness.
Specifically:
1. I converted a bunch of cases where we were emitting releases/unqualified
loads to use instead the *Operation commands that work in both modes.
2. I renamed some methods/variables that referred to releases to instead refer
to destroys.
