WIP: Enable failure aggregation globally

What does this MR do?

According to our testing guideline, aggregate_failures are encouraged when dealing with multiple assertions per test (https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#general-guidelines).

This MR is to enable this behaviour globally and remove the need of specifying explicitly at individual spec level.

Quick stats of current usages of aggregate_failures:

rg --type ruby --stats aggregate_failures .  

420 matches
420 matched lines
142 files contained matches

More info on aggregate_failures https://relishapp.com/rspec/rspec-core/docs/expectation-framework-integration/aggregating-failures

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• [-] Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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