Migrate digraph type declarations to rbs-inline #1519

Job	Run time
check-misc (head)	12s
test-memory (head)	1m 51s
test-ruby (head, master)	6m 35s
steep-check (head)	18s
test-windows (head)	1m 50s
test-ruby (3.0, master)	7m 30s
ruby-versions / Generate Ruby versions	2s
test-c (head, cc)	11s
test-c (head, gcc)	12s
test-c (head, clang)	13s
test-cpp (head, g++)	11s
test-cpp (head, clang++)	17s
test (2.5)	30s
test (2.6)	23s
test (2.7)	29s
test (3.0)	15s
test (3.1)	17s
test (3.2)	14s
test (3.3)	16s
test (3.4)	12s
test (head)	10s
	22m 8s

Provide feedback