[Fix] isLabelSyncedWithName should be nullable (#9028)

isLabelSyncedWithName should be nullable for fieldMetadata, as it is for
objectMetadata.

+ Adding missing validation on label and name sync in
fieldMetadataService for creation and update
+ adding metadata tests

packages/twenty-server/src/engine/metadata-modules/field-metadata/dtos/field-metadata.dto.ts

@@ -147,7 +147,7 @@ export class FieldMetadataDTO<
 
   @IsBoolean()
   @IsOptional()
-  @Field()
+  @Field({ nullable: true })
   isLabelSyncedWithName?: boolean;
 
   @IsDateString()