enforce test file-naming rule (#5820)

## Summary

Enforced test file naming conventions with ESLint rules and renamed 26
test files from `.spec.ts` to `.test.ts`.

## Changes

- **What**: Added ESLint rules to enforce `.spec.ts` files only in
`browser_tests/tests/` and `.test.ts` files only in `src/`
- **What**: Renamed 26 component/unit test files from `.spec.ts` to
`.test.ts` to comply with new convention

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5820-enforce-test-file-naming-rule-27b6d73d365081269b32ddcc9d3a5048)
by [Unito](https://www.unito.io)

eslint.config.ts

@@ -181,5 +181,31 @@ export default defineConfig([
         { disallowTypeAnnotations: false }
       ]
     }
+  },
+  {
+    files: ['**/*.spec.ts'],
+    ignores: ['browser_tests/tests/**/*.spec.ts'],
+    rules: {
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: 'Program',
+          message: '.spec.ts files are only allowed under browser_tests/tests/'
+        }
+      ]
+    }
+  },
+  {
+    files: ['browser_tests/tests/**/*.test.ts'],
+    rules: {
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: 'Program',
+          message:
+            '.test.ts files are not allowed in browser_tests/tests/; use .spec.ts instead'
+        }
+      ]
+    }
   }
 ])