Default to Android target-sdk-version 34, and support 35 (closes #1888)

34 is the minimum required version by Google Play, so it should be default.

Bumping to 34 and 35 requires updating both gradle-version and gradle-plugin-version.

The new versions now require an ndkVersion flag in build.gradle. This can be obtained by reading source.properties in the root of the NDK.

JDK 17 will be required for these updates. Previously required JDK 11.

templates/android/template/app/build.gradle

@@ -17,6 +17,7 @@ android {
 	compileSdkVersion Integer.parseInt(project.ANDROID_BUILD_SDK_VERSION)
 	buildToolsVersion project.ANDROID_BUILD_TOOLS_VERSION
 	::if (ANDROID_GRADLE_PLUGIN>="4.0")::ndkPath '::ANDROID_NDK_ROOT_ESCAPED::'::end::
+	::if (ANDROID_NDK_VERSION)::ndkVersion '::ANDROID_NDK_VERSION::'::end::
 
 	defaultConfig {
 		applicationId "::META_PACKAGE_NAME::"

templates/android/template/build.gradle

@@ -47,6 +47,7 @@ configure(subprojects.findAll {!it.file('build.gradle').exists() && it.file('bui
 		compileSdkVersion Integer.parseInt(project.ANDROID_BUILD_SDK_VERSION)
 		buildToolsVersion project.ANDROID_BUILD_TOOLS_VERSION
 		::if (ANDROID_GRADLE_PLUGIN>="4.0")::ndkPath '::ANDROID_NDK_ROOT_ESCAPED::'::end::
+		::if (ANDROID_NDK_VERSION)::ndkVersion '::ANDROID_NDK_VERSION::'::end::
 
 		sourceSets {
 			main {