feat: Add support for setting RuntimeClass in DevWorkspaces

[amisevsk]

What does this PR do?

Add support for setting RuntimeClass for workspaces via attribute controller.devfile.io/runtime-class. The value of this attribute is propagated directly to pods in the workspace's deployment.

Internal documentation is updated to mention this attribute.

What issues does this PR fix or reference?

Closes #788
Part of eclipse-che/che#21105

Is it tested? How?

Create DevWorkspace

cat <<EOF | oc apply -f -
apiVersion: workspace.devfile.io/v1alpha2
kind: DevWorkspace
metadata:
  name: plain
spec:
  routingClass: basic
  started: true
  template:
    attributes:
      controller.devfile.io/storage-type: ephemeral
      controller.devfile.io/runtime-class: kata
    components:
    - container:
        command:
        - tail
        - -f
        - /dev/null
        image: quay.io/amisevsk/web-terminal-tooling:dev
        memoryLimit: 512Mi
        mountSources: true
      name: web-terminal
EOF

Workspace should fail to start immediately unless kata runtime is enabled in the cluster.

PR Checklist

• E2E tests pass (when PR is ready, comment /test v8-devworkspace-operator-e2e, v8-che-happy-path to trigger)
  • v8-devworkspace-operator-e2e: DevWorkspace e2e test
  • v8-che-happy-path: Happy path for verification integration with Che

[amisevsk]

/test v8-devworkspace-operator-e2e, v8-che-happy-path

[openshift-ci]

@amisevsk: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/v8-che-happy-path	b62dadd	link	true	/test v8-che-happy-path

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[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: amisevsk, l0rd

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