feat: support controlFactory in both FormGroup and FormArray

[ahmednfwela]

Connection with issue(s)

Close #366
Connected to artflutter/reactive_forms_generator#154

Solution description

This adds a new optional controlFactory parameter to both FormGroup and FormArray.

its only responsibility is creating new controls when calling updateValue

for a usage example see the test

To Do

• Check the original issue to confirm it is fully satisfied
• Add solution description to help guide reviewers
• Add unit test to verify new or fixed behaviour
• If apply, add documentation to code properties and package readme

[ahmednfwela]

The changes are 100% backwards compatible, but if the maintainers want, I can set more sensible defaults for defaultControlFactory to create a FormGroup if the value is a Map<String, Object?>, which will simplify the usage a lot as this is a common use case