Fix nested IRB sessions' history saving (#652) #2337

Job	Run time
ruby-versions / Generate Ruby versions	3s
vterm-yamatanooroti 2.7 (latest reline)	1m 28s
vterm-yamatanooroti 2.7	1m 29s
vterm-yamatanooroti 3.0 (latest reline)	52s
vterm-yamatanooroti 3.0	1m 15s
vterm-yamatanooroti 3.1 (latest reline)	57s
vterm-yamatanooroti 3.1	49s
vterm-yamatanooroti 3.2 (latest reline)	52s
vterm-yamatanooroti 3.2	54s
vterm-yamatanooroti head (latest reline)	53s
vterm-yamatanooroti head	42s
rake test 2.7 (latest reline)	52s
rake test 2.7	54s
rake test 3.0 (latest reline)	40s
rake test 3.0	46s
rake test 3.1 (latest reline)	34s
rake test 3.1	39s
rake test 3.2 (latest reline)	30s
rake test 3.2	39s
rake test head (latest reline)	36s
rake test head	40s
rake test truffleruby-head (latest reline)	5m 56s
rake test truffleruby-head	6m 43s
	29m 43s

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