Make Delimited InputStream test more complete. #912

Job	Run time
core (5.8.1-jammy, ref/heads/main)	14m 16s
core (5.7.3-jammy, ref/heads/main)	14m 55s
core (5.6.3-focal, ref/heads/main)	14m 20s
sanitizer_testing (address, debug)	3m 37s
sanitizer_testing (address, release)	7m 31s
sanitizer_testing (thread, debug)	2m 59s
sanitizer_testing (thread, release)	5m 34s
fuzzing_regressions (debug)	2m 41s
fuzzing_regressions (release)	2m 32s
	1h 8m 25s

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