Merge pull request #23736 from seanm:c++11-simplifications

Removed all pre-C++11 code, workarounds, and branches #23736

This removes a bunch of pre-C++11 workrarounds that are no longer necessary as C++11 is now required.
It is a nice clean up and simplification.

* No longer unconditionally #include <array> in cvdef.h, include explicitly where needed
* Removed deprecated CV_NODISCARD, already unused in the codebase
* Removed some pre-C++11 workarounds, and simplified some backwards compat defines
* Removed CV_CXX_STD_ARRAY
* Removed CV_CXX_MOVE_SEMANTICS and CV_CXX_MOVE
* Removed all tests of CV_CXX11, now assume it's always true. This allowed removing a lot of dead code.
* Updated some documentation consequently.
* Removed all tests of CV_CXX11, now assume it's always true
* Fixed links.

---------

Co-authored-by: Maksim Shabunin <maksim.shabunin@gmail.com>
Co-authored-by: Alexander Smorkalov <alexander.smorkalov@xperience.ai>

modules/core/test/test_async.cpp

@@ -7,7 +7,7 @@
 
 #include <opencv2/core/bindings_utils.hpp>
 
-#if defined(CV_CXX11) && !defined(OPENCV_DISABLE_THREAD_SUPPORT)
+#if !defined(OPENCV_DISABLE_THREAD_SUPPORT)
 #include <thread>
 #include <chrono>
 #endif
@@ -85,7 +85,7 @@ TEST(Core_Async, LikePythonTest)
 }
 
 
-#if defined(CV_CXX11) && !defined(OPENCV_DISABLE_THREAD_SUPPORT)
+#if !defined(OPENCV_DISABLE_THREAD_SUPPORT)
 
 TEST(Core_Async, AsyncThread_Simple)
 {