Programs API #263
Description
Introduce a programs registry/API as teased in #243. This information has up to now been maintained in pymake but moving here could let pymake focus solely on building programs. This is in line with ongoing work to trim pymake's responsibilities, with a view to retiring it.
Devtools can maintain a registry of program repositories. As these programs are moved into GitHub repos, adopt meson, and become responsible for building/publishing themselves, devtools can make them introspectable and provide a smooth install experience. flopy's get-modflow utility is essentially a precursor to this and could relocate here. The main difference would be that instead of consuming a single combined executables distribution, it would consume releases from each of the newly independent repositories.