insight playground - allow array items to be single item (#7373)

Fixes validation for query params that can be single or multiple value.
E.g. `?contract_address=0x...&contract_address=0x..`  and `?contract_address=0x..` are both valid queries. Doing just 1 value as in the second variant did not pass validation previously, but now does

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## PR-Codex overview
This PR modifies the schema validation logic in the `blueprint-playground.client.tsx` file to handle required and optional array or single item schemas more effectively.

### Detailed summary
- Updated the return value to use `arrayOrSingleItemSchema` for both required and optional cases.
- Introduced `arraySchema` to define the structure of required arrays.
- Created `arrayOrSingleItemSchema` to combine array and single item schemas.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

- **New Features**
  - Enhanced form input flexibility to accept either a single item or an array of items for array-typed parameters.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: iuwqyir

apps/playground-web/src/app/insight/[blueprint_slug]/blueprint-playground.client.tsx

@@ -815,9 +815,13 @@ function openAPIV3ParamToZodFormSchema(
         }
 
         if (itemSchema) {
-          return isRequired
+          const arraySchema = isRequired
             ? z.array(itemSchema).min(1, { message: "Required" })
-            : z.array(itemSchema).optional();
+            : z.array(itemSchema);
+          const arrayOrSingleItemSchema = z.union([arraySchema, itemSchema]);
+          return isRequired
+            ? arrayOrSingleItemSchema
+            : arrayOrSingleItemSchema.optional();
         }
       }
       break;