[Form] Add debug:form command to debug page

Fixes #8361 partially.

Author: yceruto

debug/debugging.rst

@@ -74,6 +74,9 @@ that can help you visualize and find the information.
 
 ``debug:config``
     Shows all configured bundles, their class and their alias.
+    
+``debug:form``
+    Displays information about form types and their options.
 
 ``debug:event-dispatcher``
     Displays information about all the registered listeners in the event dispatcher.