AEP: VPA native sidecar support

[jklaw90]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Created due to #7229

This PR adds an AEP to add support for native sidecars.

Which issue(s) this PR fixes:

N/A

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

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[omerap12]

Thanks for opening this, but generally an AEP should include more detailed information.
For example, it should show what the ContainerTypeInitSidecar will look like in Go, how the ClusterFeeder will be extended, and so on.
Additionally, since this introduces a new feature, it should be guarded behind a feature gate.

I encourage you to review some of the existing AEPs to get a better sense of the expected structure and level of detail.