Step 3 - Add useFixturesFakeDate helper function

• Step 1 - Add fake_date test helper
• Step 2 - Setup useFakeDate by default in Jest
• Step 3 - Update default fake date to match rspec fixtures
• Step 3 - Add helper for useFixturesFakeDate

What does this MR do?

This MR replaces !53540 (closed) and significantly changes it's scope.

Instead of setting the default fake date to the one used in fixtures, it might be better to simple expose a helper function for specs to opt-in to this (see comment for reasoning).