Support multi-process debugging: sync breakpoints and coordinate instances #760

Job	Run time
ruby-versions / Generate Ruby versions	4s
test (3.3)	4m 27s
test (3.2)	5m 53s
test (4.0)	4m 1s
test (head)	5m 13s
test (3.4)	6m 25s
	26m 3s

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