[epic][plugin] Implement Stage Plugins

[t-kikuc]

What would you like to be added:

Support the following stages in the plugin architecture.

• WAIT Stage
  • Init server Init grpc server of wait stage plugin #5445
  • Use metadata store [WAIT] Use metadataStore in the wait stage plugin #5520
  • Core logic of waiting (without handling the stopSignal)
  • Optimize stage config location
  • Planner methods [WAIT] Implement server plan methods of Wait plugin #5504
• WAIT_APPROVAL Stage
• ANALYSIS Stage

Crossing-tasks:

• Piped) Define and handle skipOn options
• Piped&Plugin) Add Notifier methods (WaitApproval)
• Handling Skip and Approve actions on UI
  • Piped&Plugin) Handle commands of skipStage and approveStage (Analysis, WaitApproval)
  • UI&model) Add skippable flag to PipelineStage and switch by it on UI (Analysis)
  • UI&model) Add approvable flag to PipelineStage and switch by it on UI (WaitApproval)

Note: We've not determined how to support the SCRIPT_RUN Stage in the plugin architecture.

Why is this needed:

Stages will also become plugins, not built-in code.
That will extend the flexibility of pipelines.

[t-kikuc]

[ ] Piped&Plugin) Handle commands of skipStage and approveStage (Analysis, WaitApproval)
[ ] UI&model) Add skippable flag to PipelineStage and switch by it on UI (Analysis)
[ ] UI&model) Add approvable flag to PipelineStage and switch by it on UI (WaitApproval)

The overview of handling SkipStage and ApproveStage will be like this:

• Add skippable and approvable flags in the model PipelineStage.
• Set them true in BuildPipelineSyncStages() of Analysis and WaitApproval stage plugins.
• Define and use ListStageCommands() and ReportStageCommandHandled() APIs from a plugin to Piped to handle commands on the plugin side.
• On UI, show the Skip button if the stage is skippable, and show the Approve dialog if the stage is approvable

This architecture enables other plugins to use SkipStage and ApproveStage.