Update gha repos and rhino for CMS 6

[emteknetnz]

Spun off from #191

Acceptance criteria

• gha-ci uses installer 6.x-dev for CMS 6 branches
• gha-dispatch-ci runs triggers CI runs on 4.13 and 5, and not 6
• gha-merge-up merges up up correctly from 4.13 all the way to 6
• Rhino shows builds from 4.13 up to 6
• Rhino shows merge-ups from 4.13 up to 6
• CI for all commercially supported modules passes on the next major branch for all commercially supported modules - EXCEPT for any failures that are already happening on the CMS 5 branch.

Notes

• We shouldn't need a PR for gha-merge-up because based on this existing unit test it should merge-up to CMS 6 already

PRs

• ENH CMS 6 branch support rhino#12
• ENH Support for CMS 6 gha-generate-matrix#81
• ENH Handle CMS 6 branches gha-dispatch-ci#12
• FIX Do not use recipe-plugin or vendor-plugin to work out cms major gha-generate-matrix#82
• FIX Allow recipe-testing ^4 gha-ci#109
• MNT Do not look for tests in serve directory recipe-testing#17
• MNT Use frameworktest ^2 recipe-blog#50
• MNT Dev require recipe-testing dnadesign/silverstripe-elemental-userforms#90
• MNT Dev require recipe-testing silverstripe-graphql#576
• MNT Dev require recipe-testing silverstripe-elemental-bannerblock#136
• MNT Increment CI dev requirements recipe-content-blocks#39
• MNT Increment CI dev requirements silverstripe-installer#367
• MNT Use CMS 6 versions for extra jobs silverstripe-auditor#71
• DEP Remove cwp/agency-extensions recipe-kitchen-sink#54
• MNT Remove behat tests for unsupported modules silverstripe-blog#746
• FIX Ensure page has extension before calling method silverstripe-versionfeed#101
• DEP Remove remaining cwp dependencies and code recipe-kitchen-sink#55

[GuySartorelli]

Deploying rhino changes to production now (I've checked they're good in UAT).
After that's deployed I'll rerun the jobs for two affected tabs.

[GuySartorelli]

Rhino deployment to production was successful and the tabs are up to date with the new functionality.

[GuySartorelli]

PRS merged. Assigning back to steve to check everything's working as expected

[GuySartorelli]

More PRs merged. Assigning back to steve to check everything's working as expected