Allow testing of multiple VPA recommendations concurrently

[K8Y]

Which component are you using?:

vertical-pod-autoscaler

Is your feature request designed to solve a problem? If so describe the problem this feature should solve.:

This feature should allow users to deploy multiple VPAs that have the same targetRef and indicate that some VPAs are for testing only. As a result, the admission-controller and the updater should ignore these "testing" VPAs

This will make it easier to test out different VPA configurations concurrently and compare the different resulting recommendations

Describe the solution you'd like.:

The admission-controller and the updater should ignore VPAs with a label indicating a testing VPA. For example, they should ignore VPAs with the label vpaTest=true

Describe any alternative solutions you've considered.:

An alternative could be to only process VPAs that have a label that indicate they should be used; however, this solution is not chosen as it would change current behavior (all existing VPAs would need to get this label)

[K8Y]

/area vertical-pod-autoscaler