stdlib/resolv: Resolv::DNS::Resource::Generic.create returns a class #4127

Job	Run time
windows (windows-2019, ucrt)	1m 6s
test (master-nightly-focal, test)	2m 16s
windows (windows-2019, mswin)	1m 7s
test (master-nightly-focal, stdlib_test)	2m 9s
windows (windows-2022, ucrt)	1m 18s
windows (windows-2022, mswin)	1m 25s
test (master-nightly-focal, rubocop validate test_doc build test_generate_stdlib)	2m 6s
test (master-nightly-focal, lexer confirm_lexer)	3m 18s
test (master-nightly-focal, lexer compile)	3m 18s
test (3.2-dev-focal, test)	2m 15s
test (3.2-dev-focal, stdlib_test)	2m 9s
test (3.2-dev-focal, rubocop validate test_doc build test_generate_stdlib)	1m 55s
test (3.2-dev-focal, lexer confirm_lexer)	3m 11s
test (3.2-dev-focal, lexer compile)	3m 16s
test (3.1-dev-focal, test)	2m 36s
test (3.1-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 0s
test (3.1-dev-focal, lexer confirm_lexer)	3m 21s
test (3.1-dev-focal, lexer compile)	3m 16s
test (3.0-dev-focal, test)	2m 8s
test (3.0-dev-focal, rubocop validate test_doc build test_generate_stdlib)	2m 6s
test (3.0-dev-focal, lexer confirm_lexer)	3m 14s
test (3.0-dev-focal, lexer compile)	3m 14s
	52m 44s

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