`get_short_name` should return a `Cow` most likely

## What problem does this solve or what need does it fill?

`bevy_utils::get_short_name` returns a `String`. This results in unconditional allocation, even if the short name can be expressed as a slice of the full name.

## What solution would you like?

Returning a `Cow` (similarly to how [`from_utf8_lossy`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.from_utf8_lossy) works) would reduce allocation.

## What alternative(s) have you considered?

Sometimes, `get_short_name` is used for debug/display purposes. We could also provide a wrapper type that specifically implements `Display` for `&str` with the `get_short_name` heuristic to remove all type prefixes.

## Additional context

I saw a "hand made" version of `get_short_name` in a `fmt::Debug` impl in asset_v2