pattern based rewrite rule

[Roger-luo]

It is quite inconvenient to specify a pattern to match, not to say description the equivalence of a given match_and_rewrite rule. While dispatching on type signature like xDSL/MLIR is OK, I'm more leaning towards an actual pattern description language e.g

@pattern(py.Add(py.Constant(2.0), py.Add()))
def rewrite(node: ir.Statement):
    pass

the actual design probably still need a bit more thoughts but this is why I originally didn't choose to do dispatch/multiple dispatch. We should provide something like https://github.com/JuliaSymbolics/Metatheory.jl which also describes how to do bidirectional rewrite so PRs like QuEraComputing/bloqade#183 are no longer necessary.

So roughly there are decorators/objects that one can optionally use but always fallback to the most generic Python visitor if none of them applies, e.g

py.Add(py.Constant(2.0), py.Add(node)) <=> py.Mult(3.0, node)

however, we need to think about how to model this with a proper Python syntax it seems tricky doing this in Python. Could be a special rule class? e.g

class EquivRule:
    equiv_rules = {
        py.Add(py.Constant(2.0), py.Add(node)): py.Mult(3.0, node)
    }
    directional = {...}