feat(form): add support for hiding fields via lime.hidden metadata

Add support for `lime.hidden` property in form schemas to hide fields
from the UI while preserving their values in form data.

Changes:
- Add `hidden?: boolean` to LimeSchemaOptions interface
- Values are still  preserved in form state for all types (objects, arrays, primitives)
- Hidden fields don't participate in CSS grid layout

Usage:
```python
field = fields.Str(
  metadata={
    "lime": {
      "hidden": True
    }
  }
)
```

Author: jecrapo

etc/lime-elements.api.md

@@ -2559,6 +2559,7 @@ export interface LimeSchemaOptions {
     disabled?: boolean;
     // (undocumented)
     help?: string | Partial<Help>;
+    hidden?: boolean;
     layout?: LimeLayoutOptions;
 }
 

src/components/form/fields/schema-field.ts

@@ -270,6 +270,10 @@ export class SchemaField extends React.Component<FieldProps> {
     }
 
     render() {
+        if (this.props.schema.lime?.hidden) {
+            return null;
+        }
+
         if (hasCustomComponent(this.props.schema)) {
             return this.renderCustomComponent(this.props);
         }

src/components/form/form.types.ts

@@ -209,6 +209,11 @@ export interface LimeSchemaOptions {
      */
     disabled?: boolean;
 
+    /**
+     * Hide the field from the UI while preserving its value in the form data.
+     */
+    hidden?: boolean;
+
     help?: string | Partial<Help>;
 }