Fix ClassDB API portability with some android and editor classes

- `EditorNavigationMeshGenerator` was being registered as part of the Core API,
even after d3f48f88bb. We must make sure to
set Editor as the current ClassDB API type before creating an instance.

- The `VisualScriptEngineSingleton.constant` property has a property hint string
that's different between tools and non-tools builds. This commit makes the
hint string to no longer be set in `_bind_methods`, and to instead set it in
`_validate_property`. This way it's ignored when calculating the API hash.

- `JavaClassWrapper` is now registered in ClassDB on all platforms,
using a dummy implementation on platforms other than Android.
This fixes API portability between Android and other platforms.

- Updated `--class-db-json` command to ignore non-virtual methods that start
with an underscore (see: 4be87c6016).

platform/android/java_class_wrapper.cpp

@@ -28,7 +28,7 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#include "java_class_wrapper.h"
+#include "api/java_class_wrapper.h"
 #include "string_android.h"
 #include "thread_jandroid.h"
 
@@ -546,11 +546,6 @@ JavaObject::~JavaObject() {
 
 ////////////////////
 
-void JavaClassWrapper::_bind_methods() {
-
-	ClassDB::bind_method(D_METHOD("wrap", "name"), &JavaClassWrapper::wrap);
-}
-
 bool JavaClassWrapper::_get_type_sig(JNIEnv *env, jobject obj, uint32_t &sig, String &strsig) {
 
 	jstring name2 = (jstring)env->CallObjectMethod(obj, Class_getName);