Adds extractValue utility to the forms/signals/compat package. This function extracts the raw value from a FieldTree, recursively unwrapping AbstractControl instances.

It also allows to filter out only dirty/touched/enabled values or their combination to help reproduce ReactiveForms behavior.

Key Features

• Unwraps AbstractControls: Automatically resolves any AbstractControl instances in the FieldTree to their underlying values (essential for compatForm).
• Structured Filtering: Adds ExtractFilter to selectively extract fields based on state (dirty, touched, enabled).
• Array Preservation: Unlike Reactive Forms which removes filtered array items, extractValue preserves index positions by setting filtered items to undefined.

Usage

const f = compatForm(signal({first: 'Alice', last: new FormControl('Doe')}));
extractValue(f); // {first: 'Alice', last: 'Doe'}

// With filter
extractValue(f, {touched: true});