Extract integration testing helpers out of debug command tests #2297

Job	Run time
ruby-versions / Generate Ruby versions	3s
vterm-yamatanooroti 2.7 (latest reline)	1m 33s
vterm-yamatanooroti 2.7	1m 15s
vterm-yamatanooroti 3.0 (latest reline)	42s
vterm-yamatanooroti 3.0	55s
vterm-yamatanooroti 3.1 (latest reline)	58s
vterm-yamatanooroti 3.1	49s
vterm-yamatanooroti 3.2 (latest reline)	48s
vterm-yamatanooroti 3.2	1m 6s
vterm-yamatanooroti head (latest reline)	51s
vterm-yamatanooroti head	52s
rake test 2.7 (latest reline)	37s
rake test 2.7	39s
rake test 3.0 (latest reline)	23s
rake test 3.0	28s
rake test 3.1 (latest reline)	22s
rake test 3.1	19s
rake test 3.2 (latest reline)	24s
rake test 3.2	21s
rake test head (latest reline)	20s
rake test head	27s
rake test truffleruby-head (latest reline)	8m 6s
rake test truffleruby-head	7m 57s
	30m 15s

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