Autogenerate documentation for supported linux distros/versions

This MR autogenetrates documentation listing the linux distro/versions for which we generate runner/exported helper images packages.

The approach taken is identical to how the k8s docs are generated, indeed some of the same code was used. The MR includes a job to check that the docs are up to date. Since this list changes automatically when PC adds support for new distro versions, the docs could change at any time; even within an iteration. This might cause pipelines to fail in MRs with unrelated changes. We might have to allow this job to fail as a result.

Closes Use `mage packageCloud:supportedOSVersions` com... (#38363 - closed)