Remove support for Snapshot alpha and beta APIs

[PrasadG193]

Change Overview

Since VolumeSnapshot API version has already moved to v1 and set it as default (https://kubernetes.io/blog/2020/12/10/kubernetes-1.20-volume-snapshot-moves-to-ga/), the support for alpha and beta APIs becomes redundant. This PR removes support for VolumeSnapshot alpha and beta APIs

Pull request type

Please check the type of change your PR introduces:

• 🚧 Work in Progress
• 🌈 Refactoring (no functional changes, no api changes)
• 🐹 Trivial/Minor
• 🐛 Bugfix
• 🌻 Feature
• 🗺️ Documentation
• 🤖 Test
• 🏗️ Build

Issues

• fixes #issue-number

Test Plan

• 💪 Manual
• ⚡ Unit test
• 💚 E2E

[viveksinghggits]

Even if the resources are moved to v1 would people still be able to create these resources in any other version? and would that be problem for us in any way, if we merge this PR?

[PrasadG193]

@viveksinghggits after k8s 1.20, even if we try to create Snapshot with other APIs, it will be defaulted to v1 with conversion webhook. We had already done this experiment during #1979 (comment). So its guaranteed that there will be only v1 APIs present on latest clusters.

[mergify]

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