numfmt: preserve fractional digits when --from-unit is used without suffix and fixed String format

[Eshwar1440]

Fix #11663

When from-unit multiplies a fractional input with no unit suffix, uutils was rounding the result to an integer instead of preserving the fractional digits as GNU does.

Fixes conducted by making two changes in format.rs:

1. Skipped ceiling in transform_from when input has no unit suffix.
2. Used input implicit precision in format_string when not converting to a unit system.

Removed #[ignore] from the existing test so that all tests now pass.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/numfmt/numfmt. tests/numfmt/numfmt is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/date/resolution (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/expand/bounded-memory is now being skipped but was previously passing.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/expand/bounded-memory is now passing!
Congrats! The gnu test tests/tail/tail-n0f is now passing!
Congrats! The gnu test tests/unexpand/bounded-memory is now passing!

[cakebaker]

Thanks for your PR!