refator 'enqueue' scheduling action

[william-wang]

What would you like to be added:

refator enqueue scheduling action

Why is this needed:

The enqueue action is a mandatory action right now. It would be wonderful to make it optional and configurable.
Firstly the integration code with other community will be more simple and easy.
Secondly the other actions no need to depend on enqueue . All the actions are decoupled.

Actions:

1. Remove the pod admit that pod is not allowed to be created while it's podgroup is in Pending state for non-vcjob such as tfjob, spark, etc. This will make volcano integrate with upstream more easier. Previously upstream have to create podgroup, waits for podgroup entry inqueue and then create pod. This causes confused for upstream developer. What they expect is just creating podgroup which carring all of scheduling info only.
2. make the enqueue action configurable.

[shinytang6]

resolved by #2078 and #2309
/close

[volcano-sh-bot]

@shinytang6: Closing this issue.

In response to this:

resolved by #2078 and #2309
/close

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