eng formatter: support prefixes in the range argument

> Show the block only if less than 10GB is available:
>
> ```toml
> [[block]]
> block = "disk_space"
> format = " $free.eng(range:..10e9) |"
> ```

Uhh. Do we want to support prefixes in ranges? Like `range:..10Gi` and `range:..10M`.

_Originally posted by @MaxVerevkin in https://github.com/greshake/i3status-rust/issues/2043#issuecomment-2071675075_
            