Advertise PyInfo provider

[phst]

🚀 feature request

Relevant Rules

py_library, py_binary, py_test (basically all rules that consume Python files)

Description

Currently the rules don't advertise the PyInfo provider through the provides argument to the rule function (https://bazel.build/rules/lib/globals/bzl#rule.provides), which means that aspects that want to consume PyInfo can't use required_providers to restrict themselves to the Python rules, and instead have to apply to all rules.

Describe the solution you'd like

Add rule(..., provides = [PyInfo]) to the rule definitions, like e.g. https://github.com/bazelbuild/rules_python/blob/1.0.0/python/private/proto/py_proto_library.bzl#L237.

Describe alternatives you've considered

Current workaround is to check the actual presence of the provider in the aspect implementation function (if PyInfo in target). This works but is somewhat inefficient because the aspect implementation function needs to be evaluated for all rules, including non-Python ones.

[aignas]

If you would like to submit a PR to start advertising them, I would gladly review it.