refactor: add internal Promise/Future classes for future use (#521) #374

Job	Run time
release-please	13s
release-server	0s
release-server-redis	0s
release-server-provenance	0s
release-server-redis-mac-arm64	0s
release-client-mac-arm64	0s
release-client-provenance	0s
release-server-redis-mac-arm64-provenance	0s
release-client	0s
release-client-mac-arm64-provenance	0s
release-server-mac-arm64	0s
release-server-redis-provenance	0s
release-server-mac-arm64-provenance	0s
	13s

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