Enable Full Out-Of-Order Execution

[dzagieboylo]

We want to effectively allow instruction reordering at pipeline edges, which means reordering is associated with --- operators.
Then, we also need to re-establish the original order at some later point in the pipeline (a different --- boundary).

Tasks for this feature:

• syntax that wraps a "re-order" region (i.e., a start and finish). Options are "block" syntax, or "start" and "end" statements. I tend to prefer the former. We want this to be associated with two edges between pipeline stages.
• rethink existing "Out-of-order" parallel execution of branches in if statements. If these are inside of a "re-order" region, we could relax the in-order requirement part since they will get re-ordered correctly later (potentially).
• runtime implementation of a re-order buffer which checks all of the necessary blocking conditions (i.e., block statements for each entry)
• a pluggable issue scheduler that can take data from the instruction and order issue requests based on custom logic.