feat: Support stream init diagnostics events for FDv2. #338

Job	Run time
test-contract-tests	4m 28s
test-platforms-and-versions (ubuntu-latest, 17)	3m 54s
test-platforms-and-versions (ubuntu-latest, 19)	3m 40s
test-packaging	4m 51s
test-platforms-and-versions (ubuntu-latest, 11)	3m 57s
test-platforms-and-versions (ubuntu-latest, 8)	3m 51s
	24m 41s

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