Merge #11193

Merge #11193

11193: feat: Add config to replace specific proc-macros with dummy expanders r=Veykril a=Veykril

With this one can specify proc-macros from crates to expand into their input as a (temporary) workaround for the current completion problems with some of the bigger attribute proc-macros like `async_trait`.

This could've been done by just not expanding these macros, but that would require fiddling with nameres. I felt like this approach was simpler to pull off while also keeping the behaviour of the attributes/proc-macro in that they still expand instead of being dead syntax to us.

Fixes https://github.com/rust-analyzer/rust-analyzer/issues/11052

Usage(`async_trait` as example):
```jsonc
    "rust-analyzer.procMacro.dummies": {
        "async-trait": [ // crate name(as per its cargo.toml definition, not the dependency name)
            "async_trait" // exported proc-macro name
        ]
    },
```

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>