[GR-18163] Implement rb_enc_interned_str (#3706) #4986

Job	Run time
build jvm	6m 21s
build native	13m 12s
lint	13m 36s
ruby/spec on CRuby 3.0	3m 42s
ruby/spec on CRuby 3.1	3m 27s
ruby/spec on CRuby 3.2	3m 1s
fast specs	2m 10s
test integration	10m 8s
specs :truffle	14m 46s
specs :language :core	12m 43s
specs :library :cext :security :command_line :tracepoint	9m 8s
run MRI tests on native	15m 15s
test native	3m 0s
	1h 50m 29s

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