Refactor Field components with const arrow functions (#1261)

## Summary
- convert all remaining Field components to const arrow functions
- document the refactor in the CHANGELOG

## Testing
- `npm run lint`
- `npm run build`


------
https://chatgpt.com/codex/tasks/task_e_68684db1b6b88331837307a54e3f9dc1

src/components/FieldUrl.tsx

@@ -1,4 +1,3 @@
-import React from 'react'
 import InputUrl, {FieldUrlProps as InputUrlProps} from './InputUrl'
 import Block from './Block'
 
@@ -11,12 +10,12 @@ type FieldUrlProps = InputUrlProps & {
 };
 
 
-export default class FieldUrl extends React.Component<FieldUrlProps> {
-  render () {
-    return (
-      <Block label={this.props.label} fieldSpec={this.props.fieldSpec}>
-        <InputUrl {...this.props} />
-      </Block>
-    );
-  }
-}
+const FieldUrl: React.FC<FieldUrlProps> = (props) => {
+  return (
+    <Block label={props.label} fieldSpec={props.fieldSpec}>
+      <InputUrl {...props} />
+    </Block>
+  );
+};
+
+export default FieldUrl;