numfmt: add --unit-separator option for output formatting #16655

Job	Run time
Build the fuzzers	2m 41s
Build and test uufuzz examples	1m 6s
Fuzz (fuzz_test, true)	3m 32s
Fuzz (fuzz_date, true)	2m 13s
Fuzz (fuzz_split, false)	2m 40s
Fuzz (fuzz_echo, true)	2m 5s
Fuzz (fuzz_wc, false)	1m 0s
Fuzz (fuzz_env, false)	1m 2s
Fuzz (fuzz_printf, true)	2m 8s
Fuzz (fuzz_seq, false)	1m 12s
Fuzz (fuzz_tr, false)	1m 5s
Fuzz (fuzz_expr, true)	2m 6s
Fuzz (fuzz_parse_size, true)	2m 34s
Fuzz (fuzz_cut, false)	2m 30s
Fuzz (fuzz_non_utf8_paths, true)	2m 9s
Fuzz (fuzz_parse_glob, true)	3m 27s
Fuzz (fuzz_sort, false)	1m 47s
Fuzz (fuzz_cksum, false)	1m 14s
Fuzz (fuzz_parse_time, true)	2m 46s
Fuzz (fuzz_seq_parse_number, true)	2m 48s
Fuzzing Summary	6s
	42m 11s

Provide feedback