Revert "Merge branch 'create_fewer_small_strings' of https://github.com/kimono-koans/coreutils into create_fewer_small_strings"
This reverts commit 905173e1e078d8537dce4d2eaeee0d6a99fb05ff, reversing
changes made to 90812622d108ee6a8ae919cf41006bbd063ecf68.
uucore: parse_time: avoid expensive `with_scale(9)` for huge inputs
The conversion routine used to parse the time into a BigDecimal and normalize it into nanoseconds; however, for an input like 1e6666666666668320 it would require allocating a number with 6666666666668329 zeroes, which is obviously suboptimal (and redundant, as `Duration` uses `u64` for seconds).
Fixes #8634.