python3-subunit: merge inc; set PIP_INSTALL_PACKAGE

We have not supported python2 for some time now, so there is no reason
to maintain a separate python-subunit.inc file.

The wheel built by bdist_wheel is named 'python_subunit-*.whl', so set
PIP_INSALL_PACKAGE appropriately.

Add patch to use vendored _distutils from setuptools.

[YOCTO #14638]

(From OE-Core rev: 1183357dc9ebff0281c195b41f16fa07c79e84a0)

Signed-off-by: Tim Orling <tim.orling@konsulko.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/python/python3-strict-rfc3339/0001-setup.py-use-vendored-_distutils.patch

@@ -0,0 +1,27 @@
+From 857719e82daea0d85b734cac34cf569050724068 Mon Sep 17 00:00:00 2001
+From: Tim Orling <tim.orling@konsulko.com>
+Date: Sun, 20 Feb 2022 20:26:51 -0800
+Subject: [PATCH] setup.py: use vendored _distutils
+
+Deprecation warning of distutils is interferring with bdist_wheel build.
+
+For now, use the vendored setuptools._distutils.core.
+
+Upstream-Status: Pending [upstream appears unmaintained]
+
+Signed-off-by: Tim Orling <tim.orling@konsulko.com>
+---
+ setup.py | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/setup.py b/setup.py
+index 1bf87cf..a49fb8e 100644
+--- a/setup.py
++++ b/setup.py
+@@ -1,5 +1,5 @@
+ import os.path
+-from distutils.core import setup
++from setuptools._distutils.core import setup
+ 
+ readme_file = os.path.join(os.path.dirname(__file__), 'README.md')
+ readme = open(readme_file).read()