[DO NOT MERGE-WIP] migrate nightly to github actions

[anithapriyanatarajan]

Changes

Addresses the issue #2670 to migrate nightly release infrastructure from Azure to GHA with ephemeral clusters.

Core Infrastructure

1. .github/actions/setup-tekton/ - Composite action that:

   • Creates Kind cluster
   • Installs Tekton Pipeline, Triggers, and Chains
   • Configures Chains for sigstore signing with GitHub OIDC
   • Sets up namespaces and RBAC

2. .github/workflows/nightly-release-template.yml - Reusable workflow that:

   • Orchestrates the entire release process
   • Triggers existing Tekton pipelines without modification
   • Collects artifacts, logs, and execution history
   • Generates GitHub-native attestations

Project-Specific Workflows

Created individual workflows for the main projects:

• nightly-pipeline.yml - Tekton Pipeline (5am UTC)
• nightly-triggers.yml - Tekton Triggers (6am UTC)
• nightly-dashboard.yml - Tekton Dashboard (7am UTC)
• nightly-chains.yml - Tekton Chains (8am UTC)

Supporting Tools

1. Test workflow (test-tekton-setup.yml) - Validates the setup
2. Migration script (scripts/migrate-from-azure.sh) - Helps manage the transition

/kind feature

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[tekton-robot]

Skipping CI for Draft Pull Request.
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You can still manually trigger a test run with /test all

[tekton-robot]

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[afrittoli]

Thanks @anithapriyanatarajan, let me know once this is ready for review

[AlanGreene]

I realise this PR isn't marked as ready for review yet, but I have a question about the project-specific workflows.

Would it make sense to add these to the individual project repos instead of having them all run centrally in plumbing? They can still use the composite action and reusable workflow from plumbing.

Having them in the individual project repos would provide better visibility on status to maintainers and users, as well as more direct control over the nightly release config etc.

[anithapriyanatarajan]

/test all

[tekton-robot]

@anithapriyanatarajan: No jobs can be run with /test all.
The following commands are available to trigger required jobs:

• /test pull-dogfooding-mario-test
• /test pull-tekton-plumbing-check-testgrid-config

In response to this:

/test all

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