[improvement] stop using ip-holder nanode in favor of new reserved IP support

[AshleyDumaine]

NOTE

Reserved IPs are still not available on all accounts:

E0924 17:11:53.723320       1 controller.go:298] error processing service test-ns/nbless-svc (retrying with exponential backoff): failed to ensure load balancer: [404] Account doesn't have permission to access the 'Reserved IPs' feature.
I0924 17:11:53.723442       1 event.go:376] "Event occurred" object="test-ns/nbless-svc" fieldPath="" kind="Service" apiVersion="v1" type="Warning" reason="SyncLoadBalancerFailed" message="Error syncing load balancer: failed to ensure load balancer: [404] Account doesn't have permission to access the 'Reserved IPs' feature."

General:

• Have you removed all sensitive information, including but not limited to access keys and passwords?
• Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. Does your submission pass tests?
2. Have you added tests?
3. Are you addressing a single feature in this PR?
4. Are your commits atomic, addressing one change per commit?
5. Are you following the conventions of the language?
6. Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. Have you explained your rationale for why this feature is needed?
8. Have you linked your PR to an open issue

[codecov]

Codecov Report

Attention: Patch coverage is 69.69697% with 10 lines in your changes missing coverage. Please review.

Project coverage is 54.59%. Comparing base (708ee98) to head (ef21409).
Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
cloud/linode/client/mocks/mock_client.go	65.38%	9 Missing ⚠️
cloud/linode/cilium_loadbalancers.go	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #234      +/-   ##
==========================================
- Coverage   55.34%   54.59%   -0.75%     
==========================================
  Files          12       12              
  Lines        1881     1837      -44     
==========================================
- Hits         1041     1003      -38     
- Misses        696      700       +4     
+ Partials      144      134      -10     

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[AshleyDumaine]

Will reopen once reserved IP is GA