runtime-v2: hide stack trace and log location for paralle exception

[brig]

before:

18:59:33 [ERROR] (concord.yml): Error @ line: 9, col: 7. Parallel execution errors: 
com.walmartlabs.concord.svm.ParallelExecutionException: Parallel execution errors: 
Task not found: 'userDefinedExceptionTask'

Task not found: 'userDefinedExceptionTask'

	at com.walmartlabs.concord.runtime.v2.runner.vm.JoinCommand.execute(JoinCommand.java:92)
	at com.walmartlabs.concord.runtime.v2.runner.vm.StepCommand.lambda$executeWithContext$1(StepCommand.java:97)
	at com.walmartlabs.concord.runtime.v2.runner.tasks.ContextProvider.withContext(ContextProvider.java:49)
	...9 more

after:

18:59:33 [ERROR] (concord.yml): Error @ line: 9, col: 7. Parallel execution errors: 
(concord.yml): Error @ line: 16, col: 7, thread: 2: Parallel execution errors: 
(concord.yml): Error @ line: 17, col: 11, thread: 3: Task not found: 'userDefinedExceptionTask'
(concord.yml): Error @ line: 17, col: 11, thread: 5: Task not found: 'userDefinedExceptionTask'

concord.yaml:

flows:
  default:
    - call: inner                                                # line: 9
      loop:
        items: [1, 2]
        mode: parallel
        parallelism: 2

  inner:
    - parallel:                                                    # line: 16
        - task: "userDefinedExceptionTask"    # line: 17
        - log: "OK"