ci: Add osmesa to Windows GitLab CI
osmesa CI coverage on Windows was lost when Windows CI with Meson build was migrated from AppVeyor to GitLab CI
Also a build regression was introduced during osmesa classsic removal: #4119 (closed).
osmesa CI coverage on Windows was lost when Windows CI with Meson build was migrated from AppVeyor to GitLab CI
Also a build regression was introduced during osmesa classsic removal: #4119 (closed).