Migrate as much as possible to pyproject.toml

[vyasr]

This moves as much packaging information and linter configuration out of setup.[py|cfg] files into pyproject.toml with the aim of migrating to more modern Python builders in the future.

[vyasr]

@rlratzel @jakirkham the conda split recipe workaround being used for the service build is causing problems here. I'm fairly certain that the --no-index argument to pip is causing it to not use the index even for installing build dependencies (the stuff under build-system in pyproject.toml). I've tried adding them to the conda recipe in case that just works but I'm expecting it to still fail without further changes. Should we be building those packages with build isolation turned off? I believe that (in conjunction with the recipe changes) would fix the problem since then the package would be built in the environment created by conda-build that would contain the requirements specified in the recipe.

[vyasr]

Yep build isolation did it. Worked before because there was no pyproject.toml file at all so it wasn't using a PEP 518 build at all.

[jakirkham]

Yeah disabling build isolation makes sense

Normally conda-build passes this option to pip, but the recipe here runs into an edge case where these flags need to be passed manually ( conda/conda-build#3993 )

[rlratzel]

Thanks for doing this. I have some minor change requests.

[rlratzel]

/merge