[Debugger] Debugger failure when a method is called in watches and an…

…y field of the Class has the type of the field different of the value of the field because the assign was done in an unsafe way like this:

Now the datatypes check are not executed only when each field of the class is been checked before the invoke method..
_pinnable = Unsafe.As<Pinnable<T>>(array);
A unit test that reproduces the issue was created either.
Fixes mono#12374

mono/mini/debugger-agent.c

@@ -5600,7 +5600,7 @@ decode_value_internal (MonoType *t, int type, MonoDomain *domain, guint8 *addr,
 		} else if ((t->type == MONO_TYPE_GENERICINST) && 
 					mono_metadata_generic_class_is_valuetype (t->data.generic_class) &&
 					m_class_is_enumtype (t->data.generic_class->container_class)){
-			err = decode_vtype (t, domain, addr, buf, &buf, limit);
+			err = decode_vtype (t, domain, addr, buf, &buf, limit, check_field_datatype);
 			if (err != ERR_NONE)
 				return err;
 		} else {