Extensions: Vue 3 extension validation and compatibility

[aalves08]

Is your feature request related to a problem? Please describe.

Create an independent set of e2e tests that install, do tactical navigation to key areas to test changes like defineComponent and schemaDiet as examples of important steps to cover, and uninstall of extensions to make sure that they are working properly.
These e2e tests could run over-night (not in every PR) and should also cover different combinations of extensions + Rancher versions.

Interesting testing scenario:
#10659 - build extension with a "verdaccio" version of shell, then run a "simple" test spec that installs extension and goes to dashboard screen of each extension. Should capture the case of defineComponent where it was working in 2.9, but it did not work in 2.8 (leverage matrix to achieve this)

Official extensions list:

• Elemental: https://github.com/rancher/elemental-ui (Extensions compatibility tests 2.10 #11508)
• Kubewarden: https://github.com/rancher/kubewarden-ui (Add kubewarden spec to extension compatibility tests #11668)
• CAPI 🐢 : https://github.com/rancher/capi-ui-extension (still not released - only own repo)
• Neuvector: https://github.com/neuvector/manager-ext (Add Neuvector spec to extension compatibility tests #11692)
• Stackstate : https://github.com/StackVista/rancher-extension-stackstate (still not released - only own repo)

Checklist of todos:

• Have a workflow running with basic spec in 2.10 (there isn't a -head notion for 2.10)
• Have a workflow running with basic spec in 2.9 (Extensions compatibility tests 2.10 #11508)
• Have a workflow running with basic spec in 2.8 (WIP - Extensions compatibility tests 2.8 #11545)
• Have the workflow report back to our Slack (testing slack messaging workflow #11660)
• Have a workflow with a built shell version for each system

Other topics:

• Workflow can run multiple systems via matrix -> doable, test works, but there's differences in e2e tests in branches to consider...

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Additional context

[richard-cox]

@aalves08 bear in mind any PR you link to this via fixes will close it