RespondDecisionTaskFailedRequest stringer print ascii codes rather than characters

[Dom Narducci]

Describe the bug
My service has a series of tests for various workflows of the following nature:

	err = worker.ReplayWorkflowHistoryFromJSONFile(logger, "testdata/IngestWorkflow-export.json")
	require.NoError(s.T(), err)

The update from 0.12.1 to 0.13.0 revealed determinism issues (presumably from #994) being addressed independently from this ticket, but the error message printed to my logger:

replay workflow doesn't return the same result as the last event, resp: RespondDecisionTaskFailedRequest{TaskToken: [82 101 112 108 97 121 84 97 115 107 84 111 107 101 110], Cause: WORKFLOW_WORKER_UNHANDLED_FAILURE, Details: [099 111 100 101   101 120 101 099 117 116 101   108 111 099 097 108   097 099 116 105 118 105 116 121   098 108 097 104 098 108 097 104 047 119 111 114 107 102 108 111 119 115 047 097 099 116 105 118 105 116 105 101 115 046 083 105 103 110 097 108 087 105 116 104 083 116 097 114 116 087 111 114 107 102 108 111 119 065 099 116 105 118 105 116 121 044   098 117 116   104 105 115 116 111 114 121   101 118 101 110 116   102 111 117 110 100   083 105 103 110 097 108 087 105 116 104 083 116 097 114 116 087 111 114 107 102 108 111 119 065 099 116 105 118 105 116 121 044   109 097 114 107 101 114 068 097 116 097 058   123 034 097 099 116 105 118 105 116 121 073 100 034 058 034 049 034 044 034 097 099 116 105 118 105 116 121 084 121 112 101 034 058 034 083 105 103 110 097 108 087 105 116 104 083 116 097 114 116 087 111 114 107 102 108 111 119 065 099 116 105 118 105 116 121 034 044 034 114 101 112 108 097 121 084 105 109 101 034 058 034 050 048 049 057 045 048 057 045 051 048 084 049 057 058 048 054 058 049 049 046 053 054 052 057 055 055 050 052 052 090 034 125 ], Identity: replayID, BinaryChecksum: uDeploy:}, last: HistoryEvent{EventId: 14, Timestamp: 1569870371668023050, EventType: WorkflowExecutionCompleted, Version: -24, TaskId: 466901949, WorkflowExecutionCompletedEventAttributes: WorkflowExecutionCompletedEventAttributes{DecisionTaskCompletedEventId: 10}}

Do note that logger in the first code snippet is a zap logger.

To Reproduce
Is the issue reproducible?

• Yes happens every time I run these tests

Expected behavior
I expect these parts of the error to be printable as human-readable strings

Additional context
Workflow history can be provided but I would need to scrub it for private information first.