mpegvideometa: Define a Capsfeature name for MpegVideoMeta
videoparsers: mpeg2: find GstMpegVideoMeta requirementi through caps negotiation

Downstream element which requires GstMpegVideoMeta from upstream parser
should explicitly request it via caps negotiation through the
CapsFeature "meta:GstMpegVideoMeta".
videoparsers: mpeg2: Allow downstream to request for individual header parsing

Initiate an allocation query explicitly from parser which is for
allowing downstream to request for individual header parsing
since we are not guaranteed to have an allocation query from
upstream in all cases.
analyzersink: Add MpegVideoMeta Capsfeature support
analzyersink: Request mpeg2 slice headers through allocation query
codecparsers: mpegvideo: Add more fields to the GstMpegVideoSequenceHdr

Added the fields load_non_intra_quantiser_matrix and
load_chroma_intra_quantiser_matrix to the sequence header structure.
codecparsers: mpegvideo: Add vbv_delay field to PictureHeader
codecparsers: mpegvideo: Parse more slice header fields
analyzersink: Generic interface and apis to handle the codec specific details
analyzersink: Remove dead-code and other minor fixes