Significant changes to mpich port

[Marcus Calhoun-Lopez]

There is a PR (#6899) that makes significant changes to the mpich port.
The most impactful change is probably the reworking of -devel ports to make them behave more like other -devel ports.
The PR has been open for over a week, but I would be happy to keep it open if anyone would like to comment (or object).

If the mpich changes are merged, I will make similar changes to openmpi.

-Marcus

https://github.com/macports/macports-ports/pull/6899