ci: Use `cargo nextest` in integration tests

Fixes: #109


Signed-off-by: Wiktor Kwapisiewicz <wiktor@metacode.biz>

justfile

@@ -254,7 +254,7 @@ test:
     just ensure-command cargo mold
 
     if [[ "$ignored" == "true" ]]; then
-        cargo test --all -- --ignored
+        cargo nextest run --all --run-ignored ignored-only
     else
         cargo nextest run --all
         just docs