Re-apply ref: Standardize errors creation

This reverts merge request !5039 (merged), so it applies changes done in the !5027 (merged).
The revert of the changes was done because test suite in GitLab Rails app was failing due to a strict error comparison. The strict comparison of the errors returned from Gitaly RPCs now replaced with regexp matching in the gitlab!103740 (merged).
Is it still verifies the error text contains expected message, but doesn't limit it to include additional information.