fix(ui): processing and initializing form does not disable standalone fields (#11714)

The form component's `initializing` and `processing` states do not
disable fields that are rendered outside of `DocumentFields`. Fields
currently rely on the `readOnly` prop provided by `DocumentFields` and
do not subscribe to these states for themselves. This means that fields
that are rendered outright, such as within the bulk edit drawer, they do
not receive a `readOnly` prop and are therefore never disabled.

The fix is add a `disabled` property to the `useField` hook. This
subscribes to the `initializing` and `processing` states in the same way
as `DocumentFields`, however, now each field can determine its own
disabled state instead of relying solely on the `readOnly` prop. Adding
this new prop has no overhead as `processing` and `initializing` is
already being subscribed to within `useField`.

packages/richtext-slate/src/field/RichText.tsx

@@ -95,7 +95,7 @@ const RichTextField: React.FC<LoadedSlateFieldProps> = (props) => {
 
   const {
     customComponents: { Description, Error, Label } = {},
-    formInitializing,
+    disabled: disabledFromField,
     initialValue,
     setValue,
     showError,
@@ -105,7 +105,7 @@ const RichTextField: React.FC<LoadedSlateFieldProps> = (props) => {
     validate: memoizedValidate,
   })
 
-  const disabled = readOnlyFromProps || formInitializing
+  const disabled = readOnlyFromProps || disabledFromField
 
   const editor = useMemo(() => {
     let CreatedEditor = withEnterBreakOut(withHistory(withReact(createEditor())))