feat: add strong type safety for IconDefinition callbacks and support some object options

[danilo-arioli]

This PR adds full type safety to the IconDefinition schema type. Schema callbacks that use the icon field now receive correct types for the value parameter in validation, hidden, and readOnly. It also introduces the collapsible and collapsed object options to IconDefinition and adds tests covering these changes.

Before

defineField({
  name: 'icon',
  title: "Icon",
  type: 'icon',
  // ❌ Error 1: Parameter 'Rule' implicitly has an 'any' type
  // ❌ Error 2: Parameter 'value' implicitly has an 'any' type
  validation: (Rule) => Rule.custom((value) => value?.name === 'lucide:home' ? true : 'Wrong icon'),
  // ❌ value has an 'any' type
  hidden: ({value}) => value?.name === 'lucide:home' ? true : false,
  // ❌ value has an 'any' type
  readOnly: ({value}) => value?.name === 'lucide:home' ? true : false,
  options: {
    // ❌ Error: Object literal may only specify known properties, 
    // and 'collapsible' does not exist in type 'IconOptions'
    collapsible: false,
  },
})

After

defineField({
  name: 'icon',
  title: "Icon",
  type: 'icon',
  // ✅ Rule has a defined type
  // ✅ value type is automatically inferred as {name?: string} | undefined
  validation: (Rule) => Rule.custom((value) => value?.name === 'lucide:home' ? true : 'Wrong icon'),
  // ✅ value type is automatically inferred as {name?: string} | undefined
  hidden: ({value}) => value?.name === 'lucide:home' ? true : false,
  // ✅ value type is automatically inferred as {name?: string} | undefined
  readOnly: ({value}) => value?.name === 'lucide:home' ? true : false,
  options: {
    // ✅ No error - collapsible is now supported
    collapsible: false,
  },
})

[waspeer]

Thank you for this comprehensive pr!! I'll have some time hopefully tomorrow to go over it.

[danilo-arioli]

Thank you! I also added the initialValue type, which I realized I’d forgotten earlier