fix: restore --ignore-connections-limit functionality

[nornagon]

Description of Change

This restores the inadvertently removed --ignore-connections-limit functionality.

Fixes #21255.

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation is changed or added
• PR title follows semantic commit guidelines
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed --ignore-connections-limit, ironically, being ignored.

[nornagon]

This is a little tricky to write a test for because it's read at app start time, so the only way to test it would be to spin up a whole new app with the flag applied. I'd like to refactor to make this testable (and make the set of ignore-connections-limit sites modifiable at run-time, too), but I thought I'd throw this up first.

[nornagon]

win and arm failures are unrelated.

[release-clerk]

Release Notes Persisted

Fixed --ignore-connections-limit, ironically, being ignored.

[trop]

I was unable to backport this PR to "8-x-y" cleanly;
you will need to perform this backport manually.

[trop]

I was unable to backport this PR to "7-1-x" cleanly;
you will need to perform this backport manually.

[deepak1556]

@nornagon the release note 😆 💯

[trop]

@nornagon has manually backported this PR to "8-x-y", please check out #21298

[trop]

@nornagon has manually backported this PR to "7-1-x", please check out #21299