Fix handleColumns use of factory.zodInstance

The `handleColumns` used in `drizzle-zod` now uses the `zodInstance` passed in to the `factory` options.

The previous implementation caused `createSchemaFactory` to return its methods using `z.object(columnSchemas)` ignoring the custom zod instance passed to the `CreateSchemaFactoryOptions`.

Author: zanellig

drizzle-zod/src/schema.ts

@@ -59,8 +59,8 @@ function handleColumns(
 			}
 		}
 	}
-
-	return z.object(columnSchemas) as any;
+	const zod: typeof z = factory?.zodInstance ?? z;
+	return zod.object(columnSchemas) as any;
 }
 
 function handleEnum(