[AV1 Encode] Handle allocation failures safely

[fjdoria76]

Concurrent AV1/QSV workloads can exhaust system or GPU memory and currently allow allocation failures to surface as invalid-resource use or a segmentation fault. This is reported in issue #371 for Jellyfin/FFmpeg on Arc A750.

The change hardens the AV1 encode paths by:

• Translating host allocation failures into MFX_ERR_MEMORY_ALLOC.
• Cleaning up partially allocated encode-control buffers and VA buffers.
• Releasing surface references when per-task allocation fails.
• Propagating segmentation-map allocation failures.
• Converting std::bad_alloc at AV1 init, frame submission, and async execution boundaries into Media SDK errors.

Validation: git diff --check passes. An isolated CMake build was attempted but compilation is blocked in this macOS environment because va/va_version.h is unavailable.

Fixes: #371

[fjdoria76]

hi

[fjdoria76]

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