New API request: API to retrieve the list of supported decoders/encoders/vpp_features

[sreerenjb]

Currently, MediaSDK users are supposed to call MFXVideoDEcode_Query with the specific CodecId set on the input mfxVideoParam to check whether this platform/msdk has support for the codec.

Frameworks like GStreamer has a requirement to register all the supported elements to work with different available tools. For eg: "gst-inspect-1.0 msdk" should show all the supported MediaSDK decoders and encoders.
It was possible to implement it easily with libva which has vaQueryConfig APIs to retrieve the list of supported codecs.
Right now, in msdk elements, either we have to invoke MFXVideoDecode_Query n times where n is the number of known codecs. Again the same should be repeated for Encoders.
A workaround solution in middleware components is to maintain a predefined table with supported features for each intel platform and query the msdk to check the underlined platform.

Would it be better to have an API like libva where we can simply retrieve the list of supported decoders/encoders/vpp_featres?