Trigger pipelinerun manually

As a user I want to be able to trigger pipelinerun directly without being tighten up to a code flow.

Acceptance Criteria:

• Allow users to manually start a pipelinerun inside a branch 
• Add a cli option to kick of those manual events.
• Add a custom event_type (dispatch ?) to explicitly match a event kicked manually to a pipelinerun inside the target branch.
• Make it secure so other users (external or internal to the cluster) cannot kick them on behalf of the user.

Details:

• We can reuse the payload format from the VCS, for example that's a payload on push from github that we can parse and then figure things out the rest from api :

{
  "repository": {
    "html_url": "https://github.com/openshift-pipelines/pipelines-as-code"
  },
  "ref": "refs/heads/main",
  "head_commit": {
    "id": "e3327f0dbfcaa6bf9ab700c2ec5fa4a0994d8f35"
  }
}

• We can't reuse the global webhook secret since we don't want it to be shared among users, but we can have a dispatch_secret set in repo crd for the user to set and reuse.
• We can automate almost everything from a `tkn pac dispatch` command getting and setting that secret and generate an event targetting a branch or revision.
• We would just need to ask the users the eventlistenner route (which we may try to detect if user has the rights for it)
• Github Actions documentation of that same feature https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#repository_dispatch