chore(Example): upgrade Gradle and Android Gradle Plugin versions to support current flutter / dart version

Update Android build tooling:
- Bump Android Gradle Plugin from 7.3.0 to 8.1.0
- Upgrade Gradle wrapper from 7.6.3 to 8.0

Author: lukengda

example/android/gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.0-all.zip

example/android/settings.gradle

@@ -19,7 +19,7 @@ pluginManagement {
 
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
-    id "com.android.application" version "7.3.0" apply false
+    id "com.android.application" version "8.1.0" apply false
     id "org.jetbrains.kotlin.android" version "1.7.10" apply false
 }