Prospective CI fix: Run the Qt widget tests with --test-threads=1

Otherwise Qt segfault as it's not thread safe to have widgets in
different threads

.github/workflows/ci.yaml

@@ -69,11 +69,14 @@ jobs:
                   if [ ! -f ./Cargo.lock ]; then
                     cargo update -p clap --precise 4.4.18
                   fi
-            - name: Run tests
-              run: DYLD_FRAMEWORK_PATH=$Qt5_DIR/lib cargo test --verbose --all-features --workspace ${{ matrix.extra_args }} --exclude slint-node --exclude pyslint --exclude test-driver-node --exclude slint-node --exclude test-driver-nodejs --exclude test-driver-cpp --exclude mcu-board-support --exclude printerdemo_mcu --exclude uefi-demo --exclude slint-cpp
+            - name: Run tests (not qt)
+              run: DYLD_FRAMEWORK_PATH=$Qt5_DIR/lib cargo test --verbose --all-features --workspace ${{ matrix.extra_args }} --exclude slint-node --exclude pyslint --exclude test-driver-node --exclude slint-node --exclude test-driver-nodejs --exclude test-driver-cpp --exclude mcu-board-support --exclude printerdemo_mcu --exclude uefi-demo --exclude slint-cpp -- --skip=_qt::t
               env:
                   SLINT_CREATE_SCREENSHOTS: 1
               shell: bash
+            - name: Run tests (qt)
+              run: DYLD_FRAMEWORK_PATH=$Qt5_DIR/lib cargo test --verbose --all-features --workspace ${{ matrix.extra_args }} --exclude slint-node --exclude pyslint --exclude test-driver-node --exclude slint-node --exclude test-driver-nodejs --exclude test-driver-cpp --exclude mcu-board-support --exclude printerdemo_mcu --exclude uefi-demo --exclude slint-cpp --bin test-driver-rust -- _qt --test-threads=1
+              shell: bash
             - name: Archive screenshots after failed tests
               if: ${{ failure() }}
               uses: actions/upload-artifact@v4