Support multi-process debugging: sync breakpoints and coordinate instances #1806

Job	Run time
ruby-versions / Generate Ruby versions	5s
test (3.2)	1m 52s
test (debug)	6m 21s
test (3.4)	2m 0s
test (3.3)	1m 54s
test (3.0)	1m 39s
test (2.7)	1m 49s
test (head)	1m 55s
test (3.1)	1m 48s
test (4.0)	1m 53s
	21m 16s

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