Create Python Provider

[abergmeier]

The idea would be to create a Python Runtime Provider.
Using this Python Runtime Provider you could then feed the interpreter and all files necessary to py_runtime.

This way people could build/fetch their own Python via a rule.
At the same time there is no need to standardize this in rules_python.

[dayfine]

I think this is already possible: https://github.com/bazelbuild/rules_python/blob/master/proposals/2019-02-12-design-for-a-python-toolchain.md

https://github.com/bazelbuild/rules_python/blob/master/docs/python.md

[bshi]

Isn't this a duplicate of #293?

[brandjon]

#293 concerns creating a toolchain to represent a fetched Python interpreter. This issue seems to be talking about PyRuntimeInfo, which already exists (in native code) and is propagated by py_runtime_pair.

Feel free to reopen if I mischaracterized the request.