feat: Enable LocalDNS Preferred mode for K8s 1.35+

[saewoni]

Fixes #

Description
Lower enabling LocalDNS Preferred mode for k8s version 1.35+, lowered from 1.36+.
How was this change tested?

• Unit Tests

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

Release Note

[Copilot]

Pull request overview

This PR lowers the minimum Kubernetes version requirement for enabling LocalDNS in Preferred mode from 1.36+ to 1.35+. This change affects the IsLocalDNSEnabled() method implementation and adds comprehensive test coverage for both API versions.

Changes:

• Updated IsLocalDNSEnabled() method to enable LocalDNS Preferred mode for Kubernetes 1.35+ (down from 1.36+)
• Added comprehensive unit tests for LocalDNS enablement logic in both v1beta1 and v1alpha2 API versions
• Updated function documentation and inline comments to reflect the new version requirement

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
pkg/apis/v1beta1/aksnodeclass.go	Updated IsLocalDNSEnabled() to check for K8s >= 1.35 instead of >= 1.36
pkg/apis/v1alpha2/aksnodeclass.go	Updated IsLocalDNSEnabled() to check for K8s >= 1.35 instead of >= 1.36
pkg/apis/v1beta1/aksnodeclass_localdns_test.go	Added comprehensive unit tests for LocalDNS enablement logic covering all modes and version edge cases
pkg/apis/v1alpha2/aksnodeclass_localdns_test.go	Added comprehensive unit tests for LocalDNS enablement logic covering all modes and version edge cases

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[tallaxes]

@saewoni, need to update some of the tests to reflect the change (see CI). You can run them locally with make presubmit

(We should also remember to run Integration E2E tests on 1.35 - when it is available to test)