* Fixes a rather egregious bug with respect to the inability to return arbitrary objects from py::init (was causing aliasing of multiple py::object -> native instance).
* Makes Modules and Operations referencable types so that they can be reliably depended on.
* Uniques python operation instances within a context. Opens the door for further accounting.
* Next I will retrofit region and block to be dependent on the operation, and I will attempt to model the API to avoid detached regions/blocks, which will simplify things a lot (in that world, only operations can be detached).
* Added quite a bit of test coverage to check for leaks and reference issues.
* Supercedes: https://reviews.llvm.org/D87213
Differential Revision: https://reviews.llvm.org/D87958
* The binding for Type is trivial and should be non-controversial.
* The way that I define the IntegerType should serve as a pattern for what I want to do next.
* I propose defining the rest of the standard types in this fashion and then generalizing for dialect types as necessary.
* Essentially, creating/accessing a concrete Type (vs interacting with the string form) is done by "casting" to the concrete type (i.e. IntegerType can be constructed with a Type and will throw if the cast is illegal).
* This deviates from some of our previous discussions about global objects but I think produces a usable API and we should go this way.
Differential Revision: https://reviews.llvm.org/D86179
Stella Laurenzo