9751: Make `LoadCargoConfig`, `fn load_workspace_at` & `fn load_workspace` public again r=matklad a=regexident
This [commit](b24f816c0d) which restricted the visibility of `LoadCargoConfig`, `fn load_workspace_at` & `fn load_workspace` unfortunately effectively rendered every crate/tool that uses rust-analyzer as a library dead in the water.
On of such tools is [cargo-modules](https://github.com/regexident/cargo-modules), a tool for generating tree/graph visualizations of one's Rust project and is powered by rust-analyzer as a library.
For more context see the PRs that introduced those types/functions and made them `pub`:
- https://github.com/rust-analyzer/rust-analyzer/pull/7595
- https://github.com/rust-analyzer/rust-analyzer/pull/7690
If kept as is rust-analyzer would effectively no longer be usable as a library.
cc `@SomeoneToIgnore`
Co-authored-by: Vincent Esche <regexident@gmail.com>
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