GStreamer1: Update to 1.28.0

The y4menc (previously from good) and y4mdec (previously from bad)
plugins have been consolidated into y4m (now from good).

The vaapi component (multimedia/gstreamer1-vaapi) is no longer supplied
by upstream and will be removed after 2026Q1. This has been superseded by
the va plugin from 'bad', which we don't have and is rather Linux-heavy,
but no ports seem to use this anyways. Remove from makesum-all target
and adjust to be static 1.26.10 (last available) version.

Add svtav1 component to gstreamer.mk after f96400339bd6. [1]

multimedia/gstreamer1-plugins-svt-hevc has been marked DEPRECATED since
multimedia/svt-hevc is marked DEPRECATED and will be removed after
2026Q1. [1] This port does not seem to be used anywhere in the ports
tree.

Note for local patching: meson_options.txt was renamed by upstream to
meson.options across the board [2] and this change adapts to that.

Changes:
https://gstreamer.freedesktop.org/releases/1.28/

[2] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/commit/128710caab3e7521384c4c82df031702f1728af8

PR: 292706 [1]
Reported by: jbeich [1]