Ruby

Implements `#join`, `#keep_if` (#243) #386

Job	Run time
rubocop (3.3)	9s
ruby-versions / Generate Ruby versions	3s
test (3.1)	7s
test (3.2)	9s
test (3.3)	7s
test (head)	8s
test (jruby)	25s
test (jruby-head)	25s
test (truffleruby)	19s
test (truffleruby-head)	30s
	2m 22s

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