ci: Validate the experiment that retries failed tests in a new process

What does this MR do and why?

This makes the experiment described at https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1148#note_914106156 the default behavior.

Corresponding handbook MR: gitlab-com/www-gitlab-com!102538 (merged)

Related to https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/1148.

After merge

• Remove RETRY_FAILED_TESTS_IN_NEW_PROCESS from https://gitlab.com/gitlab-org/gitlab/-/settings/ci_cd
• Remove RETRY_FAILED_TESTS_IN_NEW_PROCESS from https://gitlab.com/gitlab-org/security/gitlab/-/settings/ci_cd.
• Remove RETRY_FAILED_TESTS_IN_NEW_PROCESS from https://gitlab.com/gitlab-org/gitlab-foss/-/settings/ci_cd.
• Remove RETRY_FAILED_TESTS_IN_NEW_PROCESS from https://dev.gitlab.org/gitlab/gitlab-ee/.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.