feat: Support high performance ingress with no label selector

[bcm820]

This change enables shared IP loadbalancing across all nodes whenever no bgpNodeSelector is specified; i.e. by default.

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?
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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?
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[codecov]

Codecov Report

Attention: Patch coverage is 65.62500% with 11 lines in your changes missing coverage. Please review.

Project coverage is 56.05%. Comparing base (0c600bb) to head (b00cd63).

Files	Patch %	Lines
cloud/linode/cilium_loadbalancers.go	65.62%	8 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #224      +/-   ##
==========================================
+ Coverage   55.69%   56.05%   +0.36%     
==========================================
  Files          12       12              
  Lines        1860     1873      +13     
==========================================
+ Hits         1036     1050      +14     
  Misses        680      680              
+ Partials      144      143       -1     

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[rahulait]

haven't deployed, but otherwise the changes look good to me