CI: rename the "unit test" stage to "analysis"
CI: rename the "unit test" stage to "analysis"

It doesn't run unit tests anymore; it runs coverage and cargo bench.

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/742>

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg