modified videodataset for window multiprocessing

[JK-rez]

Fixes #8322

Description

Slight workaround to VideoCapure behaviours when num worker > 0 in dataloader.
Explicitly assign video capture object to release if after reading frame. Should prevent deadlock and other cv2 errors from occurring.
Not tested exhaustively as current pipelines in CV for video pre process videos into frame beforehand. Current dataclass not scalable

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests --disttests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[ericspod]

Thanks for the update. Could we add a test to capture this issue somehow? The problem seems to be multiprocessing in Windows from what we discussed, can we add a unit test using multiprocessing to ensure this works in Windows and elsewhere? Thanks!