MDEV-25777: JAVA_INCLUDE_PATH and JAVA_INCLUDE_PATH2 not found with out of source configuration and Ninja generator

- As solution `PLUGIN_CONNECT=NO` use early check to disable plugin:
  Solution suggested by wlad@mariadb.com
- `JNI_FOUND` is a internal result variable and should be set with
cached library and header variables (like `JAVA_INCLUDE_PATH`) defined.
  * Note: wrapper cmake/FindJNI.cmake runs first time and cmake native Find<module> returns only cached variable, like `JAVA_INCLUDE_PATH`, results variable are not cached).

Reviewed by: serg@mariadb.com

Author: an3l

cmake/FindJNI.cmake

@@ -1,4 +1,4 @@
-if(JAVA_AWT_LIBRARY)
+if(JAVA_AWT_LIBRARY AND JAVA_INCLUDE_PATH)
   set(JNI_FOUND TRUE)
   return()
 endif()

storage/connect/CMakeLists.txt

@@ -13,6 +13,10 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1335 USA
 
+IF(WITHOUT_DYNAMIC_PLUGINS OR WITH_NONE OR ("${PLUGIN_CONNECT}" STREQUAL "NO"))
+  RETURN()
+ENDIF()
+
 SET(CONNECT_PLUGIN_STATIC  "connect")
 SET(CONNECT_PLUGIN_DYNAMIC "connect")