DRY the CacheString

[Wicpar]

there is a lot of redundant code in the CacheString

we could use delegate to do some of that, or other means.

[paulocsanz]

I was able to remove most implementations for CacheString on main because of Deref and DerefMut provided for it based on ArrayString.

Sadly functions that return Self or trait implementations can't be done, but honestly now the overlap is so small that I'm ok with it. I'm still open to changing that, but closing this for now as things have changed a lot.

I'm not eager to use a lot of syntax magic to avoid this small problem but I'm open to it provided you can show me a reasonable approach

[Wicpar]

yes it looks quite reasonable now