fix: Add quick fix for undersolved field diagnostic

[wyatt-herkamp]

Adds an AssistKind::QuickFix for unresolved field.

Currently, Snippets are not available for Diagnostics. So the type defaults to the Unit type if the type is not able to be inferred.

2024-03-05.08-01-15.mp4

Closes #4563

[Veykril]

Some tests would be nice to add (to check if the quickfix is available, the lines with 💡 mark those that have fixes available)

[rustbot]

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git rebase -i master
$ # delete any merge commits in the editor that appears
$ git push --force-with-lease

The following commits are merge commits:

• dc5ad65

[Veykril]

Thanks!
@bors r+

[bors]

📌 Commit 4f0bc1a has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4f0bc1a with merge a58f574...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing a58f574 to master...