python3-six: add (from oe-core)

Python 2 was end-of-lifed six years ago now, so move the python3-six
recipe from oe-core to meta-python.  Plenty of recipes still claim to
depend on it, but reviewing these is both a good way to review the
dependencies and potentially identify unmaintained packages.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-python/conf/include/ptest-packagelists-meta-python.inc

@@ -102,6 +102,7 @@ PTESTS_FAST_META_PYTHON = "\
     python3-service-identity \
     python3-setproctitle \
     python3-simpleeval \
+    python3-six \
     python3-smpplib \
     python3-soupsieve \
     python3-sqlparse \