In #10145 refactoring VideoInputStream was misplaced inside #pragma pack block resulting in broken std::string alignment = crashes on 32bit arm.

To reproduce we must hit cap_mjpeg_decoder.cpp:

cv::VideoCapture icap;
icap.open("anyfile.mp4");

crash in VideoInputStream::m_fname std::string ctor.

Existing videoio tests should catch this crash, but none of the arm32 builders run videoio tests.
I don't have an opencv test setup for arm32, is there any way to enable and run videoio tests on the CI?

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