Refactoring AutoscalerBuilder and Extracting NodeInfoComparator

[GaetanoMar96]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

This PR consolidates multiple architectural cleanups to make the AutoscalerBuilder more modular, testable with synctest, and provider-agnostic regarding node comparisons.

Key Changes:

1. Moved NewAutoscaler to autoscaler builder package.
   Moved NewAutoscaler from core/autoscaler.go to builder/autoscaler.go and created autoscaler_factory.go.
   This breaks circular dependencies and makes the
   AutoscalerBuilder more self-contained.
2. Extracting NodeInfoComparator to Individual Producers.
   Moved TemplateNodeInfoProvider and NodeInfoComparator setup logic from the multi-provider hub into individual cloud provider builders (e.g., aws.BuildAWS, gce.BuildGCE, azure.BuildAzure).
   Added generic override in NewCloudProvider for BalancingLabels when present to ensure user flags take precedence over provider defaults.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

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

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: GaetanoMar96
Once this PR has been reviewed and has the lgtm label, please assign feiskyer for approval. For more information see the Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• cluster-autoscaler/OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-ci-robot]

Hi @GaetanoMar96. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[GaetanoMar96]

/assign @towca @kawych @mtrqq