[drone] Support creating pull request and push triggers

[jimsheldon]

When creating a pipeline in Harness CI, this automation needs to create Pull Request and Push triggers.

TODO: We should also be able to support Tag and Cron events, but those will be tracked in a separate issue.

Both triggers should ignore commits with the same skip logic as Drone. While only [CI SKIP] is in the documentation, Drone supports more patterns. I only tested variations on [SKIP CI], but we should probably support ***NO_CI*** and ***no_ci*** as well.

Also, it is unclear to me if these triggers require input sets. I was unable to get either trigger working without providing an input set.

Examples

Pull Request Trigger

I think Drone only supports Open, Reopen and Synchronize pull request actions, but we should verify.

trigger:
  name: Pull Request
  identifier: pullrequest
  enabled: true
  encryptedWebhookSecretIdentifier: ""
  description: ""
  tags: {}
  orgIdentifier: default
  projectIdentifier: example
  pipelineIdentifier: example
  source:
    type: Webhook
    spec:
      type: Github
      spec:
        type: PullRequest
        spec:
          connectorRef: account.Jim_Sheldon_GitHub
          autoAbortPreviousExecutions: false
          payloadConditions:
            - key: targetBranch
              operator: Equals
              value: main
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*SKIP\ CI).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*CI\ SKIP).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*skip\ ci).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*ci\ skip).*$
          headerConditions: []
          repoName: jimsheldon/drone-sandbox
          actions:
            - Open
            - Reopen
            - Synchronize
  pipelineBranchName: <+trigger.branch>
  inputSetRefs:
    - inputs

Push Trigger

trigger:
  name: Push
  identifier: push
  enabled: true
  encryptedWebhookSecretIdentifier: ""
  description: ""
  tags: {}
  orgIdentifier: default
  projectIdentifier: example
  pipelineIdentifier: example
  source:
    type: Webhook
    spec:
      type: Github
      spec:
        type: Push
        spec:
          connectorRef: account.Jim_Sheldon_GitHub
          autoAbortPreviousExecutions: false
          payloadConditions:
            - key: targetBranch
              operator: Equals
              value: main
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*\[SKIP\ CI\]).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*\[CI\ SKIP\]).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*\[skip\ ci\]).*$
            - key: <+trigger.payload.head_commit.message>
              operator: Regex
              value: ^(?!.*\[ci\ skip\]).*$
          headerConditions: []
          repoName: jimsheldon/drone-sandbox
          actions: []
  pipelineBranchName: <+trigger.branch>
  inputSetRefs:
    - inputs