cmake: generate rtcd headers in config subdir.

Move rtcd header outputs to config subdir of config dir,
and update include sites.

Change-Id: I25c5f1808a091f3727934adc274637ebdcdcb1cf
diff --git a/test/filterintra_test.cc b/test/filterintra_test.cc
index 4c3e33f..5971349 100644
--- a/test/filterintra_test.cc
+++ b/test/filterintra_test.cc
@@ -11,7 +11,8 @@
 
 #include "third_party/googletest/src/googletest/include/gtest/gtest.h"
 
-#include "./av1_rtcd.h"
+#include "config/av1_rtcd.h"
+
 #include "test/acm_random.h"
 #include "test/clear_system_state.h"
 #include "test/register_state_check.h"