* core: improve AVX512 infrastructure by adding more CPU features groups

* cmake: use groups for AVX512 optimization flags

* core: remove gap in CPU flags enumeration

* cmake: restore default CPU_DISPATCH

fix a typo in ml_intro.md, tress -> trees

Support Convolution3D layer on IE backend (#14301)

* Add Convolution3D layer

* Disable CXX11

* Fixed tests

* Add Pooling3D layer

* Merge Conv2d with Conv3d and Pool2d with Pool3d layers

* Split pads

* Add Deconvolution layer

* Refactoring

* Deduplication

* Refactoring

* Add utils for Convolution and Pooling layers

Add solvePnPRefineLM to refine a pose according to a Levenberg-Marquardt iterative minimization process. Add solvePnPRefineVVS to refine a pose using a virtual visual servoing scheme.

properly handle "check" mode with:
"--perf_min_samples=1 --perf_force_samples=1"

* Fix for Homogenous precision #14242:
 - moved scale computation to an inline function
 - use std::numeric_limits<float>::epsilon() instead of != 0.0

* Fix for Homogenous precision #14242:
 - fixed warnings for type conversion

* Fix for Homogenous precision #14242:
 - use float epsilon() for truncation of doubles

backporting commit c9f3f4d1

BUG: Qt5 components not correctly detected if only Qt5_DIR is provided, when this is supported by Qt CMake system.

Fixed by updating Qt5 find_package call to use modern CMake syntax

Fixes: https://github.com/opencv/opencv/issues/14169

Grammatical errors for help() in detect_mser.cpp (#14122)

* Grammatical errors for help() statement

Corrected spelling of "synthetic" and added grammatical clarification for keys to press to change view or use mouse.

* Adjustment of superfluous spaces