G-API: Make test execution lighter (first attempt) #25060
### Background
G-API tests look running longer than tests for the rest of modules (e.g., 5m), and the analysis show that there's several outliers in G-API test suite which take a lot of time but don't improve the testing quality much:
In this PR I will cut the execution time to something reasonable.
### Contents
- Marked some outliers as `verylong`:
- OneVPL barrier test - pure brute force
- Stateful test in stream - in fact BG Sub accuracy test clone
- Restructured parameters instantiation in Streaming tests to generate less test configurations (54 -> 36)
### Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake
Dmitry Matveev
d792086ba6