docs: docgen underlying rules for macro-wrapped rules (#2107)

Rules that have a wrapper macro don't currently show all their
attributes because the
macro hides the rule from stardoc. This also generates docs for the
underlying rules and
has the macro reference them so that users can find all the attributes
the rule accepts.

---------

Co-authored-by: Ignas Anikevicius <240938+aignas@users.noreply.github.com>

python/py_library.bzl

diff --git a/python/py_library.bzl b/python/py_library.bzl
index 2aa797a..3b9ddd1 100644
--- a/python/py_library.bzl
+++ b/python/py_library.bzl
@@ -23,10 +23,20 @@
 _py_library_impl = _starlark_py_library if config.enable_pystar else native.py_library
 
 def py_library(**attrs):
-    """See the Bazel core [py_library](https://docs.bazel.build/versions/master/be/python.html#py_library) documentation.
+    """Creates an executable Python program.
+
+    This is the public macro wrapping the underlying rule. Args are forwarded
+    on as-is unless otherwise specified. See
+    {bzl:obj}`py_library <//python/private/common:py_library_rule_bazel.bzl%py_library>`
+    for detailed attribute documentation.
+
+    This macro affects the following args:
+    * `srcs_version`: cannot be `PY2` or `PY2ONLY`
+    * `tags`: May have special marker values added, if not already present.
 
     Args:
-      **attrs: Rule attributes
+      **attrs: Rule attributes forwarded onto
+          {bzl:obj}`py_library <//python/private/common:py_library_rule_bazel.bzl%py_library>`
     """
     if attrs.get("srcs_version") in ("PY2", "PY2ONLY"):
         fail("Python 2 is no longer supported: https://github.com/bazelbuild/rules_python/issues/886")