Rule and RuleMatcher only exist in tket2-py

[lmondada]

As mentioned today in the chat with @ABorgna and @willsimmons1465, currently the option to build pattern matchers and rewriters from rewrite rules only exists in the Python bindings.

It should probably be moved to the core tket2 repo, unless someone sees a reason why they have to be within the bindings code.

Might also be of interest to @CalMacCQ