[pmo] Eliminate non-determinism by unmixing some iteration order/sorting bisection code.

Specifically, I was abusing some sorting behavior on some arrays that I really
needed to iterate over == non-determinism. To work around these issues, I made
two changes:

1. Rather than using a bit vector to mark copy_values that were handled as part
of phi handling and thus needing a way to map copy_value -> bit vector index, I
instead just added a separate small ptr set called
copyValueProcessedWithPhiNodes.

2. I refactored/changed how copy cleanups were inserted for phi nodes by
constructing a flat 2d-array that is stable sorted by the index of the incoming
value associated with the cleanups. An incoming value's index is the count of
the copy cleanup when we see it for the first time. Thus when we do the stable
sort we will be visiting in cleanup insertion order and also will be doing
insertion order along the incomingValue axis.

Author: gottesmm