feat: Support inline context for custom and migration events #65

Job	Run time
test-contract-tests	2m 51s
test-packaging	3m 24s
test-platforms-and-versions (ubuntu-20.04, 8)	1s
test-platforms-and-versions (ubuntu-20.04, 11)	1s
test-platforms-and-versions (ubuntu-20.04, 17)	1s
test-platforms-and-versions (ubuntu-20.04, 19)	1s
	6m 19s

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