WIP: Split the controller into common and sidecar controllers - based on Snapshot Beta APIs

[xing-yang]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This PR splits the snapshot controller into two, a common controller to be deployed on the controller node, and a sidecar controller to be deployed together with the CSI driver.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:
This PR depends on the snapshot API beta changes.

Does this PR introduce a user-facing change?:

There are now a common snapshot controller and a sidecar snapshot controller. Only the sidecar controller should be deployed with the CSI driver.

[k8s-ci-robot]

@xing-yang: PR needs rebase.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: xing-yang

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[k8s-ci-robot]

@xing-yang: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-csi-external-snapshotter-1-14-on-kubernetes-1-14	9f82f7c	link	/test pull-kubernetes-csi-external-snapshotter-1-14-on-kubernetes-1-14
pull-kubernetes-csi-external-snapshotter-unit	9f82f7c	link	/test pull-kubernetes-csi-external-snapshotter-unit
pull-kubernetes-csi-external-snapshotter-1-15-on-kubernetes-1-15	9f82f7c	link	/test pull-kubernetes-csi-external-snapshotter-1-15-on-kubernetes-1-15

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[xing-yang]

Moved to #182. Close this one.