"mesh" reads much better than "me" since "me" is a different word.
There's no reason to avoid using two more characters here. Replacing
all of these at once is better than encountering it repeatedly and
doing the same change bit by bit.
The `EdgeHash` and `EdgeSet` data structures are designed specifically
as a hash of an order agnostic pair of integers. This specialization can
be achieved much more easily with the templated C++ data structures,
which gives improved performance, readability, and type safety.
This PR removes the older data structures and replaces their use with
`Map`, `Set`, or `VectorSet` depending on the situation. The changes
are mostly straightforward, but there are a few places where the old
API made the goals of the code confusing.
The last time these removed data structures were significantly changed,
they were already moving closer to the implementation of the newer
C++ data structures (aa63a87d37).
Pull Request: https://projects.blender.org/blender/blender/pulls/111391