Merge pull request #19985 from fpetrogalli:disable_threads

* [build][option] Introduce `OPENCV_DISABLE_THREAD_SUPPORT` option.

The option forces the library to build without thread support.

* update handling of OPENCV_DISABLE_THREAD_SUPPORT

- reduce amount of #if conditions

* [to squash] cmake: apply mode vars in toolchains too

Co-authored-by: Alexander Alekhin <alexander.a.alekhin@gmail.com>

modules/core/test/test_utils.cpp

@@ -8,9 +8,12 @@
 #include "opencv2/core/utils/logger.hpp"
 #include "opencv2/core/utils/buffer_area.private.hpp"
 
-#include "test_utils_tls.impl.hpp"
 #include "opencv2/core/utils/filesystem.private.hpp"
 
+#ifndef OPENCV_DISABLE_THREAD_SUPPORT
+#include "test_utils_tls.impl.hpp"
+#endif
+
 namespace opencv_test { namespace {
 
 static const char * const keys =