Move the declaration of query_config() to a dedicated header file

Declaring query_config() belongs with the query_config program, not in
ssl_test_lib.h, so move the declaration to a new header file
query_config.h.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/scripts/data_files/query_config.fmt b/scripts/data_files/query_config.fmt
index be1faef..be541cb 100644
--- a/scripts/data_files/query_config.fmt
+++ b/scripts/data_files/query_config.fmt
@@ -23,6 +23,8 @@
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#include "query_config.h"
+
 #if defined(MBEDTLS_PLATFORM_C)
 #include "mbedtls/platform.h"
 #else