test(core): enable no-floating-promises rule for tests (#11915)

Sometimes, missing `await` in the test code can cause timing issues, leading to test failures. This PR enables the `no-floating-promises` rule for the test code to ensure that such errors do not occur.

eslint.config.mjs

@@ -299,7 +299,10 @@ export default tseslint.config(
       '**/e2e/**/*',
     ],
     rules: {
-      '@typescript-eslint/no-floating-promises': 0,
+      '@typescript-eslint/no-floating-promises': [
+        'error',
+        { ignoreVoid: true },
+      ],
       '@typescript-eslint/no-misused-promises': 0,
       '@typescript-eslint/no-restricted-imports': 0,
     },