Ruby

Implement RBS prepend support with comprehensive tests #1158

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (head)	1m 8s
build (3.3)	44s
build (3.2)	42s
build (3.4)	46s
build (truffleruby-head)	34s
build (truffleruby)	34s
	4m 31s

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