(pypi) Added pip.default(unified_hub_requirements_bzl = True), which makes the unified @pypi hub generate a requirements.bzl with the per-package macros of a concrete hub‘s (requirement, whl_requirement, data_requirement and dist_info_requirement). A repo that renames its hub away from the reserved pypi name keeps its load("@pypi//:requirements.bzl", "requirement") users working, and the returned labels route through {obj}--@rules_python//python/config_settings:venv. The all_* lists are not provided, since they could only list one hub’s packages; load them from a concrete hub.