Refactor recommender to follow NewXXXController pattern

[adrianmoisey]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

This is my third attempt at #8934

This PR replaces #9156

I spent some time looking at k/k's controllers, and tried to copy that pattern. This PR isn't perfect, I think in theory any informer should be created outside of NewRecommenderController() and passed in. For VPA that's quite a lot of informers, so I tried to keep this slim.
I also tried to keep this change minimal, I plan to make more follow up PRs for the other 2 VPA components, and more tests.
I also decided against envtest, since I was looking at k/k patterns.

I also only made 1 test as an example, I plan to fill those out later.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

AI assisted

Does this PR introduce a user-facing change?

NONE

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

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[adrianmoisey]

This doesn't run under CI for now, that needs to be hooked up in the future.

[maxcao13]

general question for now, I will look at the code in more detail later:

I assume if we are trying to emulate kubernetes and we still have the plan of eventually making VPA components business loops event-driven, then we will eventually adopt their pattern of controllers and reconcilers, instead of something like controller-runtime + envtest.

[adrianmoisey]

general question for now, I will look at the code in more detail later:

I assume if we are trying to emulate kubernetes and we still have the plan of eventually making VPA components business loops event-driven, then we will eventually adopt their pattern of controllers and reconcilers, instead of something like controller-runtime + envtest.

Long term, I don't have a strong opinion either way. That's possibly something we should figure out. I don't have any controller-runtime experience.

The reason I went this direction for this PR was that I spent time familiarising myself with the patterns in k/k, and the path to getting this done in VPA became more obvious (ie: this PR).

What I'm not sure about is if this PR moves us away from controller-runtime + envtest in the future, or potentially towards that.

/hold
(Holding to ensure we get enough review on this before merging)

[adrianmoisey]

/cc iamzili
/cc omerap12