Add the CSIMigration and CSIMigrationComplete fields to the API

[xmudrii]

What this PR does / why we need it:

This PR adds the following fields to the v1beta1 API:

• CSIMigration (csiMigration) - enables CSIMigration and CSIMigration{Provider} feature flags on the API server, kube-controller-manager, and kubelets for providers that support the CSI migration
  • On Azure clusters, both CSIMigrationAzureDisk and CSIMigrationAzureFile feature gates are enabled
• CSIMigrationComplete (csiMigrationComplete) - enables the CSIMigration{Provider}Complete feature gate for providers that support the CSI migration. Enabling this feature disables fallback to the in-tree volume plugins.
  • On Azure clusters, both CSIMigrationAzureDiskComplete and CSIMigrationAzureFileComplete feature gates are enabled
  • You need to ensure that you have deployed the CSI driver on all nodes in a cluster before enabling this feature

This PR only adds the API fields. The code to enable the appropriate feature gates will be added in a follow-up PR.

This PR also adds a validation rule to ensure that CSIMigration is enabled if CSIMigrationComplete is enabled. The full config manifest has been updated to include those two fields and the appropriate descriptions.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Relevant to #616
Supersedes #1107

Does this PR introduce a user-facing change?:

Add the CSIMigration and CSIMigrationComplete fields to the API

/assign @kron4eg
/kind feature api-change

[kubermatic-bot]

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This pull-request has been approved by: xmudrii

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[kubermatic-bot]

LGTM label has been added.

Git tree hash: bf9b9fe0fabcaaefaeffcd7777a37c89d2c0cd63