Add internal copy for codecparsers and videoparsers from upstream.

This allows faster development and testing.
All the dependency to codecparsers and videoparsers will be
removed once the necessary patches reach in upstream.
Register the videoparsers statically with the application

Since we are keeping internal copy of videoparsers from
upstream gst-plugins-bad, link and register the plugins
statically with the application for now.
codecparsers: mpegvideometa: Add slice information to GstMpegVideoMeta.

This can be used by the parser elements to provide the slice level
information to downstream as per request.
videoparsers: mpeg2: Store slice information in meta if downstream requested.

Parse the slice headers and store the slice information as an array of
GstMpegVideoMetaSliceInfo with in the GstMpegVideoMeta as per
downstream request.
analyzersink: Enable mpeg2 slice parsing
videoparsers: mpegvideo: Only parse slice headers based on downstream request

If the downstream elements required extensive parsing from
the upstream parser element, then it should be requested via
metadata API specific parameters (Gst.Meta.MpegVideo)
via allocation query.