Backport of Add tests for gw proxy controller into release/1.18.x

[hc-github-team-consul-core]

Backport

This PR is auto-generated from #20510 to be assessed for backporting due to the inclusion of the label backport/1.18.

The below text is copied from the body of the original PR.

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Description

• adds some basic tests for gateway proxy controller, we should still add some more when we do further apigw work

Testing & Reproduction steps

Links

PR Checklist

• [x] updated test coverage
• [ ] external facing docs updated
• [ ] appropriate backport labels added
• [x] not a security concern

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Overview of commits

• 5eaf3b1aa2af150fe70ce602ebd6d3781c797e8f - 83afa3e63c37af638a3c7e760edf68454da52594 - 07606c02df579484a09bb524ddbb322b9f66fb4b