Windows: H.264 High 10 whose format is unknown at open still fails on D3D11VA #1532

On Windows, Decoder::open chooses D3D11VA for an H.264 stream whose pixel format is still unknown after avformat_find_stream_info (AV_PIX_FMT_NONE, for instance when the probe limit is reached before the first video packet). If that stream turns out to be High 10, 4:2:2 or 4:4:4, get_hw_format finds no D3D11 surface and decoding fails with AVERROR_INVALIDDATA, as every such stream did before #1530.

Where: crates/compositor/src/pipeline_windows.rs, d3d11va_for_stream keeps hardware for AV_PIX_FMT_NONE, and get_hw_format has no software fallback.

Possible fix: when hardware format negotiation fails, reopen the decoder on the software CpuFrames path, or let get_hw_format return the software format and route it through CpuFrames.

No file reproducing it is known yet. Found during the review of #1530 (#1530 (comment)).