Implemented QSV encode
Major updates on AVQt::EncoderQSV:
- Locks on a source as soon it gets initialized and unlocks after cleanup to prevent issues with multiple frame formats and HW contexts
- Initializes and cleans up packet sinks on registration/removal if it is running
- Stores and passes through framerate, because QSV doesn't support VFR, use VAAPI instead for this feature
- Supports zero-copy encode when input are QSV HW frames
Minor updates:
- Added libva to link_libraries in CMake config
- Player example is using the static library instead of the dynamic one
- Encoding is now enabled by default in example Player
Issue #8 is not solved by this as it only implements QSV encoding