vpa: Follow Kubernetes logging guideline

[ialidzhikov]

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.:

Currently, the logging in the VPA components does not follow the best practices and guidelines which are followed in the K8s ecosystem. VPA, as a core K8s component, should follow sig-instrumentation's Logging guide.

For example, let's take https://github.com/kubernetes/autoscaler/blob/bd8153b59d9d0da84a9d4e9b6b34e08f89b03f26/vertical-pod-autoscaler/pkg/updater/logic/updater.go#L220. The issues with this log are:

• It does not start with a capital letter. From sig-instrumentation's Logging guide: "Start from a capital letter."
• It is not a structured log. See Structured Logging.

Describe the solution you'd like.: Follow sig-instrumentation's Logging guide in the VPA's codebase.

Describe any alternative solutions you've considered.: N/A

Additional context.: N/A

[Shubham82]

/area vertical-pod-autoscaler

[Shubham82]

cc @voelzmo @kwiesmueller

[voelzmo]

/triage accepted

[omerap12]

/assign