Miscellaneous cleanup for the Android codebase:

- update gradle plugins versions
- cleanup java_godot_lib_jni

Note: logic was mostly moved around and no new logic/functionality was added.

platform/android/java/app/build.gradle

@@ -96,33 +96,33 @@ android {
         main {
             manifest.srcFile 'AndroidManifest.xml'
             java.srcDirs = [
-                    'src'
+                'src'
 //DIR_SRC_BEGIN
 //DIR_SRC_END
             ]
             res.srcDirs = [
-                    'res'
+                'res'
 //DIR_RES_BEGIN
 //DIR_RES_END
             ]
             aidl.srcDirs = [
-                    'aidl'
+                'aidl'
 //DIR_AIDL_BEGIN
 //DIR_AIDL_END
             ]
             assets.srcDirs = [
-                    'assets'
+                'assets'
 //DIR_ASSETS_BEGIN
 //DIR_ASSETS_END
             ]
         }
         debug.jniLibs.srcDirs = [
-                'libs/debug'
+            'libs/debug'
 //DIR_JNI_DEBUG_BEGIN
 //DIR_JNI_DEBUG_END
         ]
         release.jniLibs.srcDirs = [
-                'libs/release'
+            'libs/release'
 //DIR_JNI_RELEASE_BEGIN
 //DIR_JNI_RELEASE_END
         ]

platform/android/java/app/config.gradle

@@ -1,9 +1,9 @@
 ext.versions = [
-    androidGradlePlugin: '3.4.2',
-    compileSdk         : 28,
+    androidGradlePlugin: '3.6.0',
+    compileSdk         : 29,
     minSdk             : 18,
-    targetSdk          : 28,
-    buildTools         : '28.0.3',
+    targetSdk          : 29,
+    buildTools         : '29.0.1',
     supportCoreUtils   : '28.0.0',
     v4Support          : '28.0.0'
 

platform/android/java/gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.1.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip