Fix test-app tooling for RN 0.87 / Metro 0.84

- Bump @rnx-kit/metro-config to ^2.2.4: 2.1.1 called metro-config's
  exclusionList as a bare function, but Metro 0.84 changed that module to a
  { default } export, breaking `react-native start`.
- Gradle wrapper bumped to 9.3.1 by react-native-test-app 5.x's
  configureGradleWrapper during pod install (RN 0.87 alignment).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: kraenhansen

apps/test-app/android/gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.3-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.3.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

apps/test-app/package.json

@@ -33,7 +33,7 @@
     "@react-native/babel-preset": "0.87.0-nightly-20260529-88857d22f",
     "@react-native/metro-config": "0.87.0-nightly-20260529-88857d22f",
     "@react-native/typescript-config": "0.87.0-nightly-20260529-88857d22f",
-    "@rnx-kit/metro-config": "^2.1.1",
+    "@rnx-kit/metro-config": "^2.2.4",
     "@types/mocha": "^10.0.10",
     "@types/react": "^19.1.0",
     "concurrently": "^9.1.2",