The LoopSink pass doesn't actually do anything unless there's PGO profile info.
I'm interested in looking in adding an early, pre-LoopRotate aggressive LoopSink pass,
because i believe that will at the very least help to address several of vectorization failures i have analyzed.
But for that, i'll need to somehow convince LoopSink to skip profitability checks,
which results in half of the pass being conditional.
So instead, let's unsquat LoopSink pass, rename it as PGOLoopSink,
which makes room for an actual`LoopSink` pass.