Go-to-definition in Pulse DSL sometimes goes to dummy file

[gebner]

The Pulse DSL adds lots of identifiers to the id_info table with dummy ranges. When querying F* for these symbols, we get as location a file dummy with range 0:0-0:0.

[gebner]

This is an example where the issue occurs:

module IdeBug
open Pulse.Lib.Pervasives

```pulse
fn foo () requires emp returns _:unit ensures emp { () }
```

let bar () =
  foo ()
//^ go-to-definition goes to dummy here

```pulse
fn baz () requires emp returns _:unit ensures emp {
  foo ()
//^ go-to-definition goes to dummy here
}
```