Create Pipeline for running Tekton Pipeline CI/CD

[bobcatfish]

Expected Behavior

We should be testing Pipelines with Pipelines.

We should have a Pipeline which does the following, in this order (this is graph with 2 roots):

            unit tests (#532)                    build a test cluster (#534)      
                      |                                     |
     report result to github (#535)                         |
                      |                                     |
                       \                                   /
                         \                               /
          end to end tests (#533)          yaml tests (#536)      
                          | .                     |       
        report result to github (#535)   report result to github (#535)   
                           \                      /
                             teardown test cluster  (* see additional info)

("end to end tests" and "yaml tests" both execute in parallel, both depend on "build a test cluster" AND the unit test reporting results)

Runs should be triggered by new PR creation.

Actual Behavior

The CI/CD used by Tekton Pipelines (triggered via prow jobs) invokes scripts only.

Additional Info

• Should use Make Tekton Prow jobs invoke Tekton Pipelines #538 to invoke the Pipeline.
• Not sure best way to teardown cluster; probably need some way to execute a "finally" case (see Design: Conditional execution #27). For the purposes of this issue we should just make something work

[abayer]

An idea for the "teardown" task - have it be a shell script run in parallel to the two branches already defined, that periodically queries GitHub to see if the commit status has been set for the two branches, and when they are set, blows away the cluster?

[bobcatfish]

• These days dogfooding is in full swing and most issues are in https://github.com/tektoncd/plumbing
• This is the project we are using to track our current dogfooding efforts: https://github.com/orgs/tektoncd/projects/1
• This document contains our dogfooding plans