Rule-based rewriting of expressions

[xusheng6]

We should add an optimization pass to rewrite IL expressions according to a given set of rules, doing pattern matching and replacement of IL instructions to allow a sort of pseudo patching support. For example, #3881. It will also make #2043 easier, which is not very convenient to deal with right now.

Ideally, we should also allow the users to plug their own rules into the system.

This idea might has been proposed earlier and discussed internally before. I am creating this issue so we have a better point to refer to when we discuss it.

[emesare]

One real world example of this is d810 for IDA which has a very nice api for adding these rewrites https://github.com/joydo/d810/blob/master/d810/optimizers/instructions/pattern_matching/rewrite_add.py if we wanted to do these write high level python and then have it transform into some ML like IR for matching, might be more extensible then something like ISLE (cranelift).