Feature request: Expose some of the properties calculated about the float pre-output

For example [around here](https://github.com/dtolnay/ryu/blob/668d654fd67c16bbeb53e5413c97e91a41bd84e5/src/pretty/mod.rs#L70C6-L70C6) You calculate the length of the resulting decimal portion of the string

That is the specific number I am after; at the moment I am having to split the string and grab the length of the decimal portion

Some method on `ryu::Float` which exposes this property without needing to construct an entire string would be nice