docs: mention PyRuntimeInfo in PyExecutableInfo (#3573)

This is to make it more apparent how the interpreter's information can
be mixed
together with the executable info.

Related to #3181

Author: rickeylev

python/private/py_executable_info.bzl

@@ -18,6 +18,12 @@ The runfiles for the executable's "user" dependencies. These are things in e.g.
 e.g. the Python runtime itself. It's roughly akin to the files a traditional
 venv would have installed into it.
 
+:::{seealso}
+{obj}`PyRuntimeInfo` for the Python runtime files. The {obj}`py_binary` et al
+rules provide it directly so that the runtime the binary original chose
+can be accessed.
+:::
+
 :::{versionadded} VERSION_NEXT_FEATURE
 :::
 """,