* The API is a bit more verbose than I feel like it needs to be. In a follow-up I'd like to abbreviate some things and look in to creating aliases for common accessors.
* There is a lingering lifetime hazard between the module and newly added operations. We have the facilities now to solve for this but I will do that in a follow-up.
* We may need to craft a more limited API for safely referencing successors when creating operations. We need more facilities to really prove that out and should defer for now.
Differential Revision: https://reviews.llvm.org/D87996
* Removes the half-completed prior attempt at region/block mutation in favor of new approach to ownership.
* Will re-add mutation more correctly in a follow-on.
* Eliminates the detached state on blocks and regions, simplifying the ownership hierarchy.
* Adds both iterator and index based access at each level.
Differential Revision: https://reviews.llvm.org/D87982
* 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
* This is just enough to create regions/blocks and iterate over them.
* Does not yet implement the preferred iteration strategy (python pseudo containers).
* Refinements need to come after doing basic mappings of operations and values so that the whole hierarchy can be used.
Differential Revision: https://reviews.llvm.org/D86683
