sys-apps/ignition: bump to 2.17.0

[tormath1]

In this PR, we upgrade Ignition to 2.17.0 (which includes 2.16.x releases). Not so much to report regarding the upgrade itself, I followed our guide: https://github.com/flatcar/scripts/tree/main/sdk_container/src/third_party/coreos-overlay/sys-apps/ignition/files#sync-ignition-with-the-upstream

Note:

• the patch 0016-internal-exec-stages-disks-prevent-races-with-udev.patch has been dropped since it's now upstream: coreos/ignition@3f78465
• the patch about noop provider has been updated:
  • providers are now defined in init function of the package
  • noop has been renamed to metal

New providers:

• Hyper-V (it was previously a noop)
• Apple Hypervisor
• Hetzner

It also fixes an issue we had regarding SELinux relabelling.

This PR prepares for the Scaleway support.

Testing done

ebuild ignition-2.17.0.ebuild compile

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.
• CI: http://jenkins.infra.kinvolk.io:8080/job/container/job/packages_all_arches/3488/cldsv/ (all cloud providers)

Closes: flatcar/Flatcar#1261