Improve method source toggling #936

Job	Run time
lint	14s
ruby-versions / Generate Ruby versions	3s
test (3.0, ubuntu-latest)	28s
test (3.0, macos-latest)	22s
test (3.0, windows-latest)	1m 56s
test (3.1, ubuntu-latest)	30s
test (3.1, macos-latest)	21s
test (3.1, windows-latest)	1m 25s
test (3.2, ubuntu-latest)	24s
test (3.2, macos-latest)	21s
test (3.2, windows-latest)	1m 20s
test (3.3, ubuntu-latest)	26s
test (3.3, macos-latest)	30s
test (3.3, windows-latest)	2m 38s
test (head, ubuntu-latest)	34s
test (head, macos-latest)	25s
test (head, windows-latest)	1m 44s
test (jruby, ubuntu-latest)	1m 59s
test (jruby, macos-latest)	1m 28s
test (jruby-head, ubuntu-latest)	2m 6s
test (jruby-head, macos-latest)	1m 32s
test (truffleruby, ubuntu-latest)	2m 22s
test (truffleruby, macos-latest)	1m 54s
test (truffleruby-head, ubuntu-latest)	3m 5s
test (truffleruby-head, macos-latest)	2m 9s
	30m 16s

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