Fix NukeDownstream() for EVR-CP and Sync Renderer.

This commit fixes #720, #1807, #2625, #3161
Capture: Set default output file
Capture: Open capture bar automatically
Use auto everywhere for consistency
BD: Open index.bdmv directly by internal LAV and let it select playlist.
Fix DXVA status for some decoders after 4a79186.

Checking status only once is not reliable.
Even LAV Video Decoder can disable HW decoding on fly except DXVA Native mode.
Show HW decoder name in status bar.