scip: Generate symbols for local crates.
Consider something like:
```
// a.rs
pub struct Foo { .. } // Foo is "local 1"
fn something() {
crate:🅱️:Bar::new() // Bar is "local 1", but of "b.rs"
}
// b.rs
pub struct Bar { .. } // "local 1"
```
Without this there's no way to disambiguate whether "local 1" references "Bar" or "Foo".
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