Simplify and revise the execution status

[nadment]

An idea or suggestion for version 3.0: simplify and revise the execution status for pipelines and workflowd, so that it is easier for plugins to understand and use.

For pipelines, there is org.apache.hop.pipeline.engine.ComponentExecutionStatus, but nothing for workflows—just several methods:
isInitialized();
isActive();
isFinished();
isStopped();

We could have a common enum for both pipelines and workflows, even if not all states are useful.

Proposal to move the enum to the package
org.apache.hop.pipeline.engine.EngineComponent.ComponentExecutionStatus → org.apache.hop.execution.ExecutionStatus

And possibly simplify it a bit:
ComponentExecutionStatus.STATUS_RUNNING → ExecutionStatus.RUNNING
ComponentExecutionStatus.STATUS_FINISHED -> ExecutionStatus.FINISHED

This would make it easier to understand, but it is a significant API change.