test: retry proxy_spec tests that flake

[mschile]

• Closes Flaky test: address flake in proxy integration tests  #30649

Additional details

• Addressed one test that was flaking because the socket close event was already fired prior to the listener being added
• Added a retry on the generating certificates tests that appear to be flaky
• Changed the 9001 port to 2222 so it wouldn't conflict with the locally running services port

Steps to test

n/a

How has the user experience changed?

n/a

PR Tasks

• Have tests been added/updated?
• [n/a] Has a PR for user-facing changes been opened in cypress-documentation?
• [n/a] Have API changes been updated in the type definitions?

[cypress]

cypress    Run #58685

Run Properties:   Passed #58685  •  59debd4b21: test: fix proxy spec flake

Project	cypress
Branch Review	mschile/proxy_spec_flake
Run status	Passed #58685
Run duration	08m 42s
Commit	59debd4b21: test: fix proxy spec flake
Committer	Matthew Schile
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	85
View all changes introduced in this branch ↗︎

UI Coverage  45.31%
Untested elements	32
Tested elements	29

Accessibility  91.43%
Failed rules	0 critical   4 serious   0 moderate   0 minor
Failed elements	89

[cypress-bot]

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