test(e2e): update drift suite

[tallaxes]

Description

• Update E2E drift suite (among other things, adds budget and AKSNodeClass tests). Mostly aligned with AWS provider.
• Fix AKSNodeClass hashing (add KubeletConfig) and add tests

Other E2E improvements:

• Fix test AKSNodeClass overrides
• Remove drift feature gate override (no longer needed)
• Add check for leaked leases
• Override coretest.DefaultImage (pause) with MCR version, once

How was this change tested?

• make presubmit
• local E2E testing
• E2E CI: https://github.com/Azure/karpenter-provider-azure/actions/runs/12774105712 (pending)

Does this change impact docs?

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

Release Note