allow srcs in py_console_script_binary when using py_test as the binary

[BurnzZ]

This is mostly just a workaround for rules_python < 1.3.0. In bazel-contrib#2539, there was a new python -m invocation style via the main_module attribute. For instance, you can directly invoke pytest in py_test via:

py_test(
    main_module = "pytest.main",
    ...
)

However, for rules_python < 1.3.0, we need something like this:

load("@rules_python//python:py_test.bzl", "py_test")

py_console_script_binary(
    name = "test",
    args = args,
    pkg = "@pypi//pytest_bazel",
    script = "pytest_bazel",
    binary_rule = py_test,
)

However, when doing bazel query 'kind("py_test", //target:test)' --output=build, the srcs attribute of py_test would only be ["//target:rules_python_entry_point_test.py"].

This breaks some of the other rules/macros that read the srcs attribute of the py_test rule, as only the entry point is exposed, not the entire srcs of test files.