Support configuring network by NM keyfiles in cloud-init (BZ: 2118235)

BZ: 2118235

BZ: 2209349

BZ: 2196231

BZ: 2194050

BZ: 2196284

BZ: 2207716

The first two commits:
a) Commit 20c3d042b677b0c ("Revert "Manual revert "Use Network-Manager and Netplan as default renderers for RHEL and Fedora (#1465)"") and
b) Commit 5a685b281cc2d0a ("Revert "Revert "Add native NetworkManager support (#1224)"")
enables NM support in cloud-init

c) Commit 502ef3eab4809d9 ("net/sysconfig: do not use the highest autoconnect priority") is a reasonable fix to an existing downstream only change as is suggested by Thomas.
d) Commit 4bea0c43a348f20 ("net/sysconfig: cosmetic - fix tox formatting") is a cosmetic formatting fix for an existing downstream only fix to satisfy the tox tool.
e) Commits 73a171b79680846e1, 59fe487d17f554044,  e939c7dd1d98c33 and d86b5d42d7164fa89e are cherry-picks of upstream commits that fix various issues as were found by QE with NM enabled.
f) e6c2b36165d564ee8e0bf ("Set default renderer as sysconfig for c9s/RHEL 9") is downstream only commit for BZ 2209349 that is applicable for RHEL 9. It makes sysconfig the default renderer for RHEL even though nm is enabled.

The change set is tested and passed OK by QE.