Fix diagnostics in multi file projects

[sdankel]

Description

Closes #5027

Now instead of caching the Diagnostics object, we cache a mapping of file path -> Diagnostics

When we publish diagnostics, we only publishing the diagnostics for the given URI, not for the entire project. I added a test where there are no diagnostics in the main.sw file, but a bunch of diagnostics in the other files in the project.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[JoshuaBatty]

Just tested this locally, wow I can't believe how bad it was! We need to get this in the beta-4 release for sure. Thanks for spotting this error! So much nicer now.

[JoshuaBatty]

Awesome work