[12.x] Add default parameter support to Request::fluent() method

[michaelnabil230]

Summary

This PR enhances the fluent() method in the Request class to support a default value when the requested input is missing. This improves the developer experience and prevents potential null-related issues.

Changes

• Updated method signature to accept a second parameter: $default = [].
• Modified method logic to return the provided default value when the input key is absent.
• Ensures Fluent always receives a valid array structure.

[AhmedGamal905]

Much needed