Support the property CAP_PROP_SETTINGS under linux

[Alan-li]

System information (version)

• OpenCV => 4.2
• Operating System / Platform =>Ubuntu 18.04:
• Compiler => Qt Creator 4.11.0

Detailed description

when I use Videocapture , I want to use the property CAP_PROP_SETTINGS , but it was only support windows direct show , Do you consider support this property under linux .

Steps to reproduce

Issue submission checklist

• I report the issue, it's not a question
• I checked the problem with documentation, FAQ, open issues,
  answers.opencv.org, Stack Overflow, etc and have not found solution
• I updated to latest OpenCV version and the issue is still there
• There is reproducer code and related data files: videos, images, onnx, etc

[alalek]

In case of DShow important part of this functionality has been provided by underlying capturing SDK itself.
We really don't want to explode code base of OpenCV implementing similar stuff.
So large patches with more than 100 LOC would be rejected.
Another question is missing infrastructure for automated UI tests (no plans to invest into that).

[paroj]

So large patches with more than 100 LOC would be rejected.

should be doable within this budget by relying on https://docs.opencv.org/4.2.0/dc/d46/group__highgui__qt.html