Add resolver plugin diagnostics

[MonicaOlejniczak]

↪️ Pull Request

These changes map resolver errors in the rust resolver plugin to diagnostic errors:

• Add to_diagnostic_error in the resolver plugin to map resolver errors
• Add CodeFrame from helper when only the file path is known
• Add #[builder(setter(into))] to the diagnostic message, so string slices can be passed in
• Fix diagnostic_error! handling of simple messages, so that a diagnostic is actually returns instead of a plain anyhow error
• Update memory file system to write directories when files are written, so that the resolver checks work as expected in the resolver plugin tests
• Return File in JsonError to avoid additional fs reading

Note that hints and alternative modules have not been implemented

🚨 Test instructions

cargo test