More advanced group_imports with 4 groups and adaptable "std-like" crates

[DrSloth]

In code i write i have taken to group the import statements into 4 groups:

1. "std-like" crates which include all the normal std crates (std, alloc, core) and large crates like tokio or frameworks like axum or bevy pretty much everything which fundamentaly controls how my code will look like.
2. Other external crates
3. Workspace internal crates
4. Crate internal imports

I have thought about trying to implement this in rustfmt, but i don't know how doable this is.
I guess making crates in 1. optionally configurable shouldn't be that hard, but does rustfmt get any workspace information? Is it feasible to optionally implement retrieving workspace information for such a feature, or would this require some larger architectural/conceptual change?

Thanks in advance :)

[ytmimi]

rustfmt only operates on the AST provided by the rustc parser and doesn't get any information that would help it determine the difference between local and external crates in a consistent way.

Some related issues: #4693, #4709, #4788