[CI] Add tests run step (for seq backend)

Author: EgorOrachyov

.github/workflows/ubuntu.yml

@@ -55,4 +55,9 @@ jobs:
 
       - name: Build library sources
         working-directory: ${{ env.build_dir }}
-        run: cmake --build . --target all --verbose -j `nproc`
+        run: cmake --build . --target all --verbose -j `nproc`
+
+      - name: Run unit-tests (sequential backend)
+        working-directory: ${{ env.build_dir }}
+        run: bash scripts/tests_run_all.sh
+        shell: bash