Refactor `scalers` package

[zroubalik]

Proposal

We should slightly refactor scalers package, it is hard to create subpackages there (for example pkg/scalers/aws, pkg/scalers/...) that needs to use ScalerConfig. Because this introduces circular dependency.

We should move ScalerConfig out and refactore the package a little bit.

Use-Case

No response

Is this a feature you are interested in implementing yourself?

Yes

Anything else?

No response