Support boosting CPU during the pod startup in VPA

[laoj2]

Which component are you using?:

vertical-pod-autoscaler

/area vertical-pod-autoscaler

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

Long application start time is a known problem for more traditional workloads running in containerized applications, especially Java workloads. This delay can negatively impact the user experience and overall application performance. One potential solution is to provide additional CPU resources to pods during their startup phase, but this can lead to waste if the extra CPU resources are not set back to their original values after the pods are ready.

We're proposing to allow VPA to boost the CPU request and limit of containers during the pod startup and to scale the CPU resources back down when the pod is Ready, leveraging the in-place pod resize Kubernetes feature.

Describe the solution you'd like.:

Draft AEP: #7863

[laoj2]

/assign @raywainman
/assign @voelzmo

cc @jpawelczak