Improve build-test-smart-contracts CI

[abizjak]

Task description

There is the following TODO in the build-test-smart-contracts.yaml file

  "cargo_test_example_contracts":
    name: ${{ matrix.example-contract }} cargo:test
    runs-on: ubuntu-latest
    strategy:
      matrix:
        example-contract:
          - 'counter'
          # removed because test fail with "implement me"
          # - 'escrow'
          
          # the following 2 contracts fail to build due to:
          # error: building tests with panic=abort is not supported without `-Zpanic_abort_tests`
          # - 'fib'
          # - 'lockup'
          
          #Remaining example contracts have not yet been added to ci
    steps:
      - name: Checkout
        uses: actions/checkout@v4
      - name: Test
        working-directory: smart-contracts/rust-contracts/example-contracts/${{ matrix.example-contract }}
        run: |
          git config --global url."https://github.com/".insteadOf "[email protected]:"
          rustup default ${{ env.RUST_CLIPPY }}
          cargo test --target x86_64-unknown-linux-gnu

We should add the remaining example contracts to the list.