ci: add Artifact Hub lint checks

[vdemeester]

Changes

• Add parallel Artifact Hub lint jobs for the Task and StepAction catalogs.
• Fetch complete history and tags for Git-based Tekton versioning.
• Exclude v1.0.1 and v1.2.0 from the ephemeral Task-lint checkout: those immutable tags contain manifests labelled 1.0.0 and 1.1.0 respectively.
• Pin Artifact Hub CLI to v1.23.0, configure Git safe-directory access, and include both checks in the CI summary.

Submitter Checklist

• Includes tests for new or changed functionality
  • Validated both ah lint commands against a clean full clone using artifacthub/ah:v1.23.0.
• Includes docs for user-facing changes
  • Not applicable: CI-only change.
• Commit messages follow best practices
• Meets the Tekton contributor standards

Release Notes

NONE

[tekton-robot]

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