Run PushRuleCheck in parallel

Merged Robert May requested to merge parallel-push-check into master

What does this MR do?

Runs the push checks in parallel because they are IO-heavy.

Related to #222247 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • Label as security and @ mention @gitlab-com/gl-security/appsec
  • The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • Security reports checked/validated by a reviewer from the AppSec team
Edited by Robert May