#7421430 Goals Capture: Enable Goals Step i2 layout based on the feature flag

Proposed Changes

This PR enables Goals Step i2 layout based on the feature flag signup/goals-step-2:

• Creates a GoalsCaptureContainer component, which conditionally renders the one column layout if the flag is disabled and the two columns layout if the flag is enabled
• Applies the GoalsCaptureContainer on GoalsStep component, defining the displayAllGoals as true if the flag is enabled
  • Updates useEffect to not delete the DIFM and Import goals when the flag is true
• Restores the i2 styling in the scss file, but now it’s specified for a .two-columns parent selector
• Updates the SelectGoals component to render the UI based on the flag
  • If true: renders the “Select all that apply” hint on top of the goals list
  • If false: renders the bottom links for DIFM and Import

Testing Instructions

Testing with the flag enabled

1. Navigate to http://calypso.localhost:3000/setup/goals?siteSlug=<YOUR-SITE>&flags=signup/goals-step-2
2. Check if the two columns layout appears as expected

3. Check if the mobile layout appears as expected

4. Select DIFM and Import goals and refresh the page
5. Check if the selected goals persisted

Testing with the flag disabled

1. Navigate to http://calypso.localhost:3000/setup/goals?siteSlug=<YOUR-SITE>
2. Check if the one column layout appears as expected

3. Check if the mobile layout appears as expected

Related to #64997