ts: basic documentation for utility scripts

This reverts commit a630ad73.

Onnx conformance tests

* Add ONNX conformance tests

* dnn(test): add filters for ONNX conformance tests

* add filter lists for OCV backend

* address review comments

* move test_clip_inbounds to all_denylist

* address clip issue

* avoid empty lists
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>

resolves #21038

* remove C assert

* revert C header

* fix several points in review

* fix test_ds.cpp

* [ts][summary.py] Extend `-o` to support tabs separated output.

* [ts][summary.py] Improve TABS sepatated output.

There is no need to print TAB at the beginning and at the end of each
row in the table.

Cosmetic change: using python list comprehension instead of for loop
to process a single row.

- cache value, evaluate once
- better support for MINGW
- anything in 'cv' namespace
- test: dump number of active threads

- CMake option: OPENCV_DNN_IE_NN_BUILDER_2019

backport commit 659ffadd

* Support ARM64 Windows 10 platform

* Fixed detection issue for ARM64 Windows 10

* Try enabling ARM NEON intrin

* build: disable NEON with MSVC compiler

* samples(directx): gdi32 dependency

dnn(eltwise): fix handling of different number of channels

* dnn(test): reproducer for Eltwise layer issue from PR16063

* dnn(eltwise): rework support for inputs with different channels

* dnn(eltwise): get rid of finalize(), variableChannels

* dnn(eltwise): update input sorting by number of channels

- do not swap inputs if number of channels are same after truncation

* dnn(test): skip "shortcut" with batch size 2 on MYRIAD targets

* Support nGraph

* Fix resize

- apply tag 'skip_other'

* imgproc: fix bit-exact GaussianBlur() / sepFilter2D()

- avoid kernels with bad approximation
- GaussiabBlur - apply error-diffusion approximation for kernel (8-bit fraction)

* java(test): update features2d ref data

* test: update test_facedetect

If tests are run through GTest option `--gtest_also_run_disabled_tests`

- IPP/SSE4.2 works well

detected by UBSAN

Found using `codespell -q 3 -S ./3rdparty -L activ,amin,ang,atleast,childs,dof,endwhile,halfs,hist,iff,nd,od,uint`

backporting of commit: ec43292e

misused 'optional' mode

Usage example:
- run.py -a -t java --package=calib3d

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

similar to '--test_require_data' parameter