Add hook for customizing the debug representation of an object #3226

Job	Run time
ruby-versions / Generate Ruby versions	2s
test (2.7)	3m 55s
test (3.0)	3m 57s
test (3.1)	4m 13s
test (3.2)	5m 46s
test (3.3)	5m 48s
test (debug)	13m 20s
test (head)	6m 18s
	43m 19s

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