[fix] Removing Stale DNS Entries

[bren-ak]

What this PR does / why we need it:

• Add a watch to the LinodeCluster controller for Machine objects.
• Remove getMachineIPs for getDNSMachineIPs to remove duplicate list creation and ensure accurate stale record deletions.

The added watch for Machine objects to the LinodeCluster helps improve the timing of DNS record clean ups as the LinodeMachine does not get a call for deletion until the node has been drained. In addition the change to the function for DNS list entries to be removed has been modified to be built off of the state of Machine objects being deleted rather than completely deleted LinodeMachines (where the finalizer has been removed and the object is gone).

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 39 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.25%. Comparing base (f4e2145) to head (643cac1).

Files with missing lines	Patch %	Lines
...nal/controller/linodecluster_controller_helpers.go	0.00%	27 Missing ⚠️
internal/controller/linodecluster_controller.go	0.00%	12 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1083      +/-   ##
==========================================
+ Coverage   69.23%   69.25%   +0.01%     
==========================================
  Files          71       71              
  Lines        6566     6589      +23     
==========================================
+ Hits         4546     4563      +17     
- Misses       1725     1735      +10     
+ Partials      295      291       -4     

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[Copilot]

Pull request overview

This PR improves DNS load balancer record cleanup for LinodeClusters by reconciling earlier during CAPI Machine deletion and by basing stale DNS pruning on the “current desired” DNS entry set (excluding deleting Machines), reducing the chance of leaving stale A/AAAA records behind.

Changes:

• Add a Machine watch to the LinodeCluster controller to trigger reconciliation when Machines enter deletion.
• Refactor stale DNS cleanup (Linode + Akamai) to use the computed dnsEntries list rather than rebuilding IP lists from LinodeMachine state.
• Add a unit test ensuring stale Linode DNS records are deleted for deleting CAPI Machines.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
internal/controller/linodecluster_controller.go	Adds a Machine watch with predicates to trigger LinodeCluster reconciliation during Machine deletion.
internal/controller/linodecluster_controller_helpers.go	Adds mapping from Machine events to the corresponding LinodeCluster reconcile request.
cloud/services/domains.go	Refactors stale DNS deletion logic to use desired dnsEntries (and removes the older IP-list builder).
cloud/services/domains_test.go	Adds a unit test validating stale Linode DNS record deletion when a CAPI Machine is deleting.

[komer3]

LGTM!