Fixes #39653 - Remove Puppet 6 references

[jakduch]

Puppet 6 reached EOL in 2023. Remove its version-specific host parameters, repository setup, package references, and documentation from provisioning templates.

This also updates the documented minimum version to Puppet 7 and makes Puppet 8 the unconditional FreeBSD package after the Puppet 6 option is removed.

Stack

Depends on #10928. Until that PR is merged, Assert Single Commit is expected to report the preceding Puppet 5 commit as well.

Verification

• compiled every changed ERB template
• checked the complete active provisioning-template tree for remaining Puppet 6 references
• verified the resulting Puppet 7 and Puppet 8 repository paths
• verified Puppet 8 is present in the supported FreeBSD 14.4 and 15.1 release ports branches
• full test suite runs in CI

AI assistance

This pull request was prepared with assistance from Codex 5.6 Sol High.

[jakduch]

This is stacked on #10928, so the single-commit check is expected to fail until #10928 is merged. After that, this PR will contain only the #39653 commit.

[adamruzicka]

This is stacked on

pr processor will be confused from this :)

Now that p5 removal is in, could you please rebase?

[jakduch]

Rebased, thanks!

[adamruzicka]

I opened a community post to lay out the broader picture and what I was aiming for with the 6 & 7 removal issues.

I'm fine with this, but I'll let it sit until tomorrow to give other people a chance to chime in.

[d1nuc0m]

Please wait until #10816 is merged, I'm reviewing it

[adamruzicka]

This now needs a rebase

[jakduch]

The container build failed while downloading CentOS Stream 9 BaseOS metadata (a checksum mismatch followed by mirror connection failures), before reaching the Foreman changes. This looks like a transient mirror/infrastructure issue.

[jakduch]

All other checks have passed, including the Ruby, JavaScript, Katello, RPM, RuboCop, and single-commit checks. Only the infrastructure-related container build remains. Could someone with permission please rerun that check?

[d1nuc0m]

@jakduch just amend/force push again (ik, it's the whole pipeline but it's faster)