Enhance clusteradm so that user can submit workload to target cluster directly

[suigh]

There is no way for an user to submit workload to the target managed cluster directly now, the user has to write some codes to get information from placementdecision, analyse it and then forword workoad to the target cluster, this is inconvenient.

A draft idea is to enhance clusteradm, then user can submit workload like following:

1. User submit workload with “clusteradm submit-workload xxx.yaml --placement abc”
2. Clusteradm checks the managed cluster candidate in the specified placement, then forward the xxx.yaml to the target cluster by clusternet or manifestwork.
3. The managed cluster will create the xxx.yaml, the workload in xxx.yaml will run on it.

[openshift-ci]

@qiujian16: The label(s) kind/enhancement cannot be applied, because the repository doesn't have them.

In response to this:

/kind enhancement

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[qiujian16]

/kind feature

[zychina]

And also use need a way to query workload status to have a e2e scenario, issue I opened before #78