Add UI test for RateLimitPolicy form view

[emmaaroche]

Details

RateLimitPolicy form has: policy name, target gateway, limits with counters/conditions.

Checklist

• Policy name required field validation
• Target gateway selector validation
• Add limit functionality
• Limit counters configuration
• Limit conditions configuration
• Remove limit functionality
• Form/YAML toggle preserves data
• Form submission creates resource
• Edit mode loads existing resource