gitlab-ci: Move classic driver testing to a new meson-classic job

The motivation is to allow llvmpipe to be enabled instead in the
meson-i386 job.

v2: (Eric Engestrom)
* Rename meson-main job to meson-gallium
* Remove stale comment above meson-i386 job

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4166>
1 file changed