test(jspg): rename items fixture to array and resolve unused HashMap warning

- Rename fixtures/items.json to fixtures/array.json to better reflect array testing constraints.
- Update reference paths in src/tests/fixtures.rs and across other fixture JSON files.
- Remove unused HashMap import in src/validator/rules/dict.rs to resolve the compiler warning.

fixtures/dynamicType.json

@@ -164,8 +164,8 @@
             {
               "code": "DYNAMIC_TYPE_RESOLUTION_FAILED",
               "values": {
-                "discriminator": "kind",
-                "pointer": "$kind.filter"
+                "pointer": "$kind.filter",
+                "discriminator": "kind"
               },
               "details": {
                 "path": "filter",