Merge pull request #25042 from mshabunin:doc-upgrade

Documentation transition to fresh Doxygen #25042

* current Doxygen version is 1.10, but we will use 1.9.8 for now due to issue with snippets (https://github.com/doxygen/doxygen/pull/10584)
* Doxyfile adapted to new version
* MathJax updated to 3.x
* `@relates` instructions removed temporarily due to issue in Doxygen (to avoid warnings)
* refactored matx.hpp - extracted matx.inl.hpp
* opencv_contrib - https://github.com/opencv/opencv_contrib/pull/3638

modules/videoio/doc/videoio_overview.markdown

@@ -1,12 +1,14 @@
 Video I/O with OpenCV Overview {#videoio_overview}
-===================================
+==============================
 
-### See also:
+@tableofcontents
+
+@sa
   - @ref videoio "Video I/O Code Reference"
   - Tutorials: @ref tutorial_table_of_content_app
 
 General Information
-===================
+-------------------
 
 The OpenCV @ref videoio module is a set of classes and functions to read and write video or images sequence.
 
@@ -53,10 +55,11 @@ cv::VideoCapture cap(filename, cv::CAP_MSMF);
 //or specify the apiPreference with open
 cap.open(filename, cv::CAP_MSMF);
 ```
-
 @sa cv::VideoCapture::open() , cv::VideoCapture::VideoCapture()
 
-#### How to enable backends
+
+How to enable backends
+----------------------
 
 There are two kinds of videoio backends: built-in backends and plugins which will be loaded at runtime (since OpenCV 4.1.0). Use functions cv::videoio_registry::getBackends, cv::videoio_registry::hasBackend and cv::videoio_registry::getBackendName to check actual presence of backend during runtime.
 
@@ -71,7 +74,9 @@ To enable dynamically-loaded videoio backend (currently supported: GStreamer and
 
 @note Don't forget to clean CMake cache when switching between these two modes
 
-#### Use 3rd party drivers or cameras
+
+Use 3rd party drivers or cameras
+--------------------------------
 
 Many industrial cameras or some video I/O devices don't provide standard driver interfaces
 for the operating system. Thus you can't use  VideoCapture or VideoWriter with these devices.
@@ -83,6 +88,7 @@ It is a common case that these libraries read/write images from/to a memory buff
 possible to make a `Mat` header for memory buffer (user-allocated data) and process it
 in-place using OpenCV functions. See cv::Mat::Mat() for more details.
 
+
 The FFmpeg library
 ------------------