Epic: kpt pipeline implementation

[droot]

Following tasks need to be accomplished as part of this umbrella issue.

• Core hydration DAG machinery (without setters): This involves reading the pipeline, invoking different function groups, function execution with the args from pipeline, recursive hydration, resources input/output chains, leaf level hydration etc.
• Implement support for docker function execution Implement support for docker function execution #1334 add container runtime for pipeline #1355
• e2e test framework
• e2e tests for majority of the common use-cases
• In-place sink-mode with merge as default Merge strategy
• Resource pruning (in-place) kpt fn render should support resource pruning #1524
• Structured Result Support Standardize structured function results (ResourceList.results) #1390
• Out-place sink-mode support kpt fn render should support out-of-place sink-mode #1412
• Wire the CLI command with kpt docs machinery and command help/usage
• End user documentation

[droot]

/cc @mikebz @mortent @frankfarzan @Shell32-Natsu @phanimarupaka

[frankfarzan]

Closing this since the remaining issue is tracked as well.