Onnx conformance tests

* Add ONNX conformance tests

* dnn(onnx): make conformance stubs a part of repository
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>

Add regression test for QRcode encoding and decoding
Co-authored-by: NAPrigarina <ann73617@gmail.com>

add test case for "tf/reduce_sum"

* fix output dimension of reduce_sum

* add test case and fix bug

* add more cases

* style:change files name

* fix a little bug

DNN: Test data of biasadd in tf_importer

* Add files via upload

* Update generate_tf_models.py

tests for Normalize subgraph, Slice, Mul and Expand

* another fix opencv/opencv#20575

* download_models: rename downloaded content for further investigation
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>

add humanseg model and test data

* add test data for LSTM w/ activations

* dnn: put lstm_cntk_tanh testdata in opencv_extra
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>