Deduplicate compiler warnings based on their source location

[TomAFrench]

After #6926 we still get a number of cases where multiple instances of the same compiler warning/error is emitted pointing at the same line of source code. This tends to just make the output harder to read for very little benefit so I'm inclined to deduplicate these so that we only print them once.

[jfecher]

What are some examples of this?

[TomAFrench]

I think the case where this comes up most frequently is on comptime functions. If you run nargo check on aztec-nr then you should see it. For instance I get the below as part of the warnings emitted.

warning: index is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- index is private
   │

warning: offset is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- offset is private
   │

warning: length is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- length is private
   │

warning: index is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- index is private
   │

warning: offset is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- offset is private
   │

warning: length is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- length is private
   │

warning: index is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- index is private
   │

warning: offset is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- offset is private
   │

warning: length is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- length is private
   │

warning: trait `traits::Empty` which provides `empty` is implemented but not in scope, please import it
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ -------
   │

warning: trait `note::note_interface::NoteInterface` which provides `get_note_type_id` is implemented but not in scope, please import it
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ -------
   │

warning: from_field_unsafe is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- from_field_unsafe is private
   │

warning: from_field_unsafe is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- from_field_unsafe is private
   │

warning: from_field_unsafe is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- from_field_unsafe is private
   │

warning: from_field_unsafe is private and not visible from the current module
   ┌─ value-note/src/value_note.nr:21:1
   │
21 │ #[note]
   │ ------- from_field_unsafe is private
   │