add a "Messages" tab to `WorkflowInvocationState` if > 1 messages #1073

Job	Run time
build-client / build-client	9m 16s
setup-selenium / setup_chromedriver	3s
Test (3.8, 0)	42m 30s
Test (3.8, 1)	48m 2s
Test (3.8, 2)	48m 1s
	2h 27m 52s

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