use ByteSize for byte size rendering / parsing, add same to duration

[syphar]

This started of as a part of the new docs_rs_build CLI, where I wanted to parse & render byte-sizes & durations consistently.

The lead to doing that for docs_rs_admin too, which will make my life easier when using the admin CLI to work with crate limits.

Then I thought about configuration, where the .env files will also be much easier to read when we use human-readable values for durations & sizes.

Then I fixed all the errors. Also, the Duration type offers some nice constructors since rust 1.91, so I changed that where I saw it. The docs_rs_env_vars change was necessary to handle the Err type from ByteSize / FromStr with our helpers.

These are not yet all places, and not yet the perfect design (I tried to prevent a ByteSize newtype for now).

[syphar]

r? @GuillaumeGomez

[GuillaumeGomez]

Is it really worth it to add a new dependency for a type we could implement in less than 100 lines?

[syphar]

Is it really worth it to add a new dependency for a type we could implement in less than 100 lines?

I admit I can't judge the compile time difference, it's probably more than these 100 lines with the parsing & rendering, but even when it's 300/400 lines, plus tests?

[GuillaumeGomez]

I don't even think we need 100 lines. We need gb, mb and b constructors. And we can implement Deref (or repr(transparent), this one might be better in this case) on it and basically we have all we need.

[syphar]

I don't even think we need 100 lines. We need gb, mb and b constructors. And we can implement Deref (or repr(transparent), this one might be better in this case) on it and basically we have all we need.

I replaced the external crate with a simplified custom implementation, with less unnecessary features or speed, and with two added things that the lib didn't have.