[FEATURE] Use pypa/build to generate project metadata locally from any build system

[dholth]

Is your feature request related to a problem? Please describe.
Use pypa/build to get project metadata in a standard, build-system-independent way.

Additional context
Grayskull should be able to generate a recipe for a local project without referring to pypi, and without requiring a specific build system or pyproject.toml layout. Use pypa/build to generate the project's metadata, then shuffle that data into the recipe.

#541