fix(dd): ensure full block writes to handle partial writes to slow pipes #16558

Job	Run time
Build and test uufuzz examples	1m 15s
Build the fuzzers	2m 47s
Fuzz (fuzz_seq, false)	1m 12s
Fuzz (fuzz_expr, true)	2m 15s
Fuzz (fuzz_printf, true)	2m 14s
Fuzz (fuzz_sort, false)	1m 47s
Fuzz (fuzz_date, true)	2m 12s
Fuzz (fuzz_split, false)	1m 41s
Fuzz (fuzz_parse_glob, true)	1m 59s
Fuzz (fuzz_echo, true)	2m 3s
Fuzz (fuzz_seq_parse_number, true)	1m 17s
Fuzz (fuzz_test, true)	2m 11s
Fuzz (fuzz_wc, false)	1m 10s
Fuzz (fuzz_cut, false)	1m 5s
Fuzz (fuzz_cksum, false)	1m 10s
Fuzz (fuzz_tr, false)	1m 53s
Fuzz (fuzz_parse_size, true)	1m 2s
Fuzz (fuzz_non_utf8_paths, true)	2m 9s
Fuzz (fuzz_parse_time, true)	1m 13s
Fuzz (fuzz_env, false)	1m 10s
Fuzzing Summary	6s
	33m 51s

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