runtime-v2: add exceptions to ParallelExecutionException

[amithkb]

  - try:
    - task: "throw"
      in:
        exception: "BOOM${item}"
        payload:
          key: "${item}"
    loop:
      items:
        - 1
        - 2
      mode: parallel
      parallelism: 2
    error:
      - log: ${lastError.cause.exceptions.stream().map(x -> x.cause.payload).toList()}     # prints [{key=1}, {key=2}]

[brig]

added payload to parallel exception last error: