AWS CodePipeline (codepipeline) implementation for FakeCloud.
awsJson1.1 control plane for CodePipeline: pipelines and their versions,
pipeline/action/rule executions, custom action types, webhooks, job and
third-party-job polling, stage transitions, approvals, and resource
tagging. There is no real release engine, so a StartPipelineExecution
mints a pipeline execution that lazily settles from InProgress to a
terminal Succeeded state on the reads that surface it
(GetPipelineExecution, GetPipelineState, ListPipelineExecutions) --
the same deterministic settle pattern CodeDeploy and CodeBuild use.
Everything else is real, persisted, account-partitioned CRUD.