Scaffold IPC-based API (#711) #1

Job	Run time
build	2m 46s
extension	31s
format	2m 23s
generate	3m 32s
smoke	4m 32s
tidy	39s
lint (ubuntu-latest)	4m 19s
misc	39s
lint (macos-latest)	3m 58s
test (race mode)	1d 0h 0m 0s
test (no submodules)	4m 13s
test (concurrent test programs)	7m 51s
lint (noembed)	4m 22s
lint (windows-latest)	12m 0s
test (windows-latest)	13m 58s
test (ubuntu-latest)	7m 36s
test (macos-latest)	5m 49s
baselines	5m 51s
test (noembed)	5m 6s
required	3s
	1d 1h 30m 8s

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