Refactor kitchen.yml and update openSUSE Leap from 15.1 => 15.3

[myii]

What does this PR do?

Clean up kitchen.yml, including less duplication and modernisation:

• Use the most common run_command of /usr/lib/systemd/systemd as a general setting.
• Remove unnecessary entries:
  • image for Fedora.
  • salt_bootstrap_options for openSUSE and Arch Linux.
• Use driver instead of driver_config:
  • Modern test kitchen examples should only use driver, not driver_config test-kitchen/kitchen-azurerm#69
  • test-kitchen/kitchen-azurerm@55b768d
• Update openSUSE Leap platform from 15.1 to 15.3.
• Use YAML node anchors to remove further duplication:
  • Both Fedora and openSUSE provision_command entries are all duplicates that have been DRYed.

I kept the YAML node anchors change as a separate commit in case it needs to be removed; understandably, some folks prefer to avoid them.

[myii]

Only unexpected CI failures are the FreeBSD jobs. I've submitted #1574 as a fix for those.