Refactor SourceFinder #2270

Job	Run time
ruby-versions / Generate Ruby versions	1s
vterm-yamatanooroti 2.7 (latest reline)	1m 23s
vterm-yamatanooroti 2.7	1m 21s
vterm-yamatanooroti 3.0 (latest reline)	1m 4s
vterm-yamatanooroti 3.0	45s
vterm-yamatanooroti 3.1 (latest reline)	55s
vterm-yamatanooroti 3.1	59s
vterm-yamatanooroti 3.2 (latest reline)	43s
vterm-yamatanooroti 3.2	56s
vterm-yamatanooroti head (latest reline)	42s
vterm-yamatanooroti head	57s
rake test 2.7 (latest reline)	41s
rake test 2.7	50s
rake test 3.0 (latest reline)	29s
rake test 3.0	36s
rake test 3.1 (latest reline)	36s
rake test 3.1	36s
rake test 3.2 (latest reline)	26s
rake test 3.2	37s
rake test head (latest reline)	26s
rake test head	30s
rake test truffleruby-head (latest reline)	6m 54s
rake test truffleruby-head	5m 52s
	28m 19s

Provide feedback