Prevent seed-boostrap to delete Shoot VPA RBAC

[ialidzhikov]

How to categorize this PR?

/area auto-scaling
/kind bug
/priority normal

What this PR does / why we need it:
Currently for a Shoot cluster which is registered as Seed, the seed controller wrongly deletes VPA RBAC from the cluster when the Shoot hasspec.kubernetes.verticalPodAutoscaler.enabled=true and the corresponding Seed has
spec.settings.verticalPodAutoscaler.enabled=false.
The Shoot cluster SystemComponentsHealthy is constantly flapping (caused by the 2 control loops acting on the same resource - seed controller deleting it and gardener-resource-manager creating it):

    - type: SystemComponentsHealthy
      status: 'False'
      lastTransitionTime: '2020-07-29T11:55:26Z'
      lastUpdateTime: '2020-07-29T11:57:26Z'
      reason: ClusterRoleMissing
      message: 'Required ClusterRole "system:evictioner" in namespace "" is missing.'

This PR adds the cluster type (shoot or seed) as part of the VPA RBAC name and in this way prevents the issue.

Release note:

An issue causing the seed controller to delete VPA RBAC for ShootedSeed is now fixed.

[rfranzke]

/lgtm