DevOps Pipeline - External Integrations

### Description

In talking with @robmarcer, and hearing from other customers about their requests for Pipeline features, we have an opportunity to extend Pipelines way beyond just pushing from one Instance to another. This Epic captures various steps we can take to improve the Pipeline feature set:

- Allow multiple "actions" per stage of a pipeline
- Provide a "Webhook" action in a Pipeline
- Provide a GitHub action in a Pipeline

### Which customers would this be available to

Team + Enterprise Tiers (EE)