bd0c2344f2
fix(ide-db): correct single-file module rename
Fixes a bug where rust-analyzer would emit `WorkspaceEdit`s with paths to dirs instead of files for the following project layout.
lib.rs
```rust
mod foo;
```
foo.rs
```rust
mod bar {
struct Bar;
}
```
Also fixes emitted paths for modules with mod.rs.
The bug resulted in panic in helix editor when attempting to rename a module.