Handle checkPermission() below api 23

Although Qt 6 supports API 23+, it's still not bad to do this fix, it
achieves two things:
* Avoid the use of reflection when checking for permission state
* It works for all api versions

With this we would be sure we don't need to do a check in c++

if (androidSdkVersion < 23)
    return true;

The platform api checks if permission is granted or not, irrelevant of
the api version.

Change-Id: I9766dc35bbc8347ad0d60fde54b95710c8866736
Reviewed-by: Alex Blasche <[email protected]>

src/android/jar/src/org/qtproject/qt/android/QtNative.java

@@ -843,13 +843,8 @@ public static int checkSelfPermission(String permission)
         int perm = PackageManager.PERMISSION_DENIED;
         synchronized (m_mainActivityMutex) {
             Context context = getContext();
-            try {
-                if (m_checkSelfPermissionMethod == null)
-                    m_checkSelfPermissionMethod = Context.class.getMethod("checkSelfPermission", String.class);
-                perm = (Integer)m_checkSelfPermissionMethod.invoke(context, permission);
-            } catch (Exception e) {
-                e.printStackTrace();
-            }
+            PackageManager pm = context.getPackageManager();
+            perm = pm.checkPermission(permission, context.getPackageName());
         }
 
         return perm;