CI: External contributions are not distributed properly causing long and flaky builds

[ZachJW34]

Current behavior

Tests are doubled up on CI for external contributors, see build. We ran into this problem pre-10.0 but did't apply the same test distribution rules to our new 10.0 tests #21305. This can lead to long and flaky builds for external contributors.

That job isn't the only one that is duplicating tests, so an audit of the this build should be made to find all the jobs that are not distributing properly.

Desired behavior

CI should distribute tests properly for 10.0 builds

Test code to reproduce

Check out an external contributors CI build

Cypress Version

10.1.0

Other

No response

[cypress-bot]

The code for this is done in cypress-io/cypress#22326, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[emilyrohrbough]

This change has been completed. It's associated with the 10.3.0 release though there was no user-facing changes related to this change.