fix(richtext-lexical): various issues for lexical sub-fields due to incorrectly generated client field schema map (#10276)

Fixes https://github.com/payloadcms/payload/issues/9905,
https://github.com/payloadcms/payload/issues/9660

Single lexical fields were represented file in the schema map (`path =>
field`). In the client schema map however, they were incorrectly
represented like this: `path => { fields: [field] } `

test/fields/seed.ts

@@ -481,6 +481,28 @@ export const seed = async (_payload: Payload) => {
   await _payload.create({
     collection: 'LexicalInBlock',
     data: {
+      content: {
+        root: {
+          children: [
+            {
+              format: '',
+              type: 'block',
+              version: 2,
+              fields: {
+                id: '6773773284be8978db7a498d',
+                lexicalInBlock: textToLexicalJSON({ text: 'text' }),
+                blockName: '',
+                blockType: 'blockInLexical',
+              },
+            },
+          ],
+          direction: null,
+          format: '',
+          indent: 0,
+          type: 'root',
+          version: 1,
+        },
+      },
       blocks: [
         {
           blockType: 'lexicalInBlock2',