Support IELR(1) Parser Generation #1400

Job	Run time
steep-check (head)	12s
test-memory (head)	35s
check-misc (head)	11s
test-ruby (head, master)	6m 5s
test-windows (head)	2m 4s
test-ruby (3.0, master)	6m 5s
ruby-versions / Generate Ruby versions	3s
test-cpp (head, g++)	13s
test-cpp (head, clang++)	19s
test (2.5)	24s
test (2.6)	27s
test (2.7)	28s
test (3.0)	13s
test (3.1)	13s
test (3.2)	15s
test (3.3)	15s
test (head)	17s
	18m 19s

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