Replace all inclusions of config.h

Also remove preprocessor logic for MBEDTLS_CONFIG_FILE, since
build_info.h alreadyy handles it.

This commit was generated using the following script:

# ========================
#!/bin/sh
git ls-files | grep -v '^include/mbedtls/build_info\.h$' | xargs sed -b -E -i '
/^#if !?defined\(MBEDTLS_CONFIG_FILE\)/i#include "mbedtls/build_info.h"
//,/^#endif/d
'
# ========================

Signed-off-by: Bence Szépkúti <bence.szepkuti@arm.com>
diff --git a/tests/include/test/helpers.h b/tests/include/test/helpers.h
index c0d2c00..27e5599 100644
--- a/tests/include/test/helpers.h
+++ b/tests/include/test/helpers.h
@@ -30,11 +30,7 @@
  * directly (without using the MBEDTLS_PRIVATE wrapper). */
 #define MBEDTLS_ALLOW_PRIVATE_ACCESS
 
-#if !defined(MBEDTLS_CONFIG_FILE)
-#include "mbedtls/config.h"
-#else
-#include MBEDTLS_CONFIG_FILE
-#endif
+#include "mbedtls/build_info.h"
 
 #if defined(MBEDTLS_THREADING_C) && defined(MBEDTLS_THREADING_PTHREAD) && \
     defined(MBEDTLS_TEST_HOOKS)