Pull-request capabilities in GitHub interceptor

Epic Goal

Make additional capabilities available in the GitHub interceptor in Tekton Triggers. These capabilities are currently available as custom interceptors that are used in the upstream CI for the Tekton project itself:
https://github.com/tektoncd/plumbing/tree/main/tekton/ci/interceptors

Scenarios

• As a DevOps engineer, I want to filter GitHub events based on files that have changed in the pull-request so that pipelines execute only for relevant changes in the Git repository.
• As a DevOps engineer, I want to be able to approve pull-requests before a pipeline starts executing for it so that I can limit pipeline execution to legitimate pull-requests coming from known sources.

Acceptance Criteria

• The following capabilities are available in the GitHub interceptor in Tekton Triggers
  • Filtering pull-requests events based on files changed
  • OWNERS files support for approving pull-requests before executing pipelines
• GitHub interceptor with the above capabilities can be used with OpenShift Pipelines

Previous Work:

• Upstream Tekton pluming

Open questions::

• TBD

Done Checklist

• Acceptance criteria are met
• Non-functional properties of the Feature have been validated (such as performance, resource, UX, security or privacy aspects)
• User Journey automation is delivered
• Support and SRE teams are provided with enough skills to support the feature in production environment