QRCodeDetector::decodeMulti() fixed invalid usage fixedType()

* fixed invalid usage fixedType()
changed default barcode type to CV_8UC1
added tests
added assert in case multi channel straight barcode input

* deleted extra wrap into OutputArray

* fix warnings

* objdetect(qr): remove unnecessary checks
Co-authored-by: NAlexander Alekhin <alexander.a.alekhin@gmail.com>

* add LeakyRelu to tf-importer

* fix whitespace error

* added test for leakyrelu

they might be thrown from third-party code (notably Ogre in the ovis
module).
While Linux is kind enough to print them, they cause instant termination
on Windows.
Arguably, they do not origin from OpenCV itself, but still this helps
understanding what went wrong when calling an OpenCV function.

* Fix error in documentation for RGB->HSV convertion

* Update colors.markdown

Instead of being a copy of line 76, line 79 instead correctly indicates that it will show a histogram for a gray image in curve mode, as given by the code block at line 103 referencing image "gray" instead of image "im".

* fix opencv/opencv#19402

* Fixed bug with constant Div

* Supported constant mul and div for inputs with different shapes

  * follow the review comment

- reuse g_isOpenCLAvailable variable instead