Support `asdf shell latest:version`

### Is your feature request related to a problem? Please describe

`asdf local ` and `asdf global ` support two formats for version setting: `` (`20.0.0`) and `latest[:]` (`latest:20`), but `asdf shell` supports only first one.

It's not quite clear why only one command doesn't support `latest:` prefix making it a bit inconsistent. When switching between versions and relying on prefix you would expect it to work with all three.

### Describe the proposed solution

Add support of `asdf shell latest[:]` so it will be consistent with other two version set commands.

### Describe similar `asdf` features and why they are not sufficient

`asdf local` and `asdf global` modify `.tool-version` file so they're not much of replacement. Shell completion helps but when relying on shell history it still requires manually editing version (ex. `asdf shell nodejs 20.0.0` -> `asdf shell nodejs 20.1.0`).

### Describe other workarounds you've considered

Tried wrapping `asdf list-all` to resolve latest version, it works but quite slow sometimes:

```bash
function asdf-shell-latest() {
asdf shell "$1" "$(asdf list-all "$1" "$2" | tail -n1)"
}

# sets ruby version to 2.7.8 as latest available
asdf-shell-latest ruby 2.7
```

Start at the `asdf shell` command entry point and compare its version handling with `asdf local` and `asdf global`; use the `asdf list-all` behavior described in the issue as the reference for resolving `latest[:]`. Verify that `asdf shell` accepts both version forms and applies the selected version only to the current shell.

Written by the indexing model from the issue text.