improvement: shared diagnostics between compiler and language server

[baszalmstra]

This PR introduces the mun_diagnostics crate. This crate provides the Diagnostic trait which is used by both the compiler and the language server to provide the same detailed diagnotics. The crate enables conversion from hir::Diagnostic to mun_diagnostics::Diagnostic which also adds more detailed information (which first resided in the compiler itself).

The compiler uses the Diagnostic trait to convert it to a Snippet from annotate_snippets to emit the diagnostic information to the console.

The language server uses the Diagnostic trait to convert it to a lsp_types::Diagnostic which is send to the language server client.

This enables sharing a lot of the logic of diagnostics between these two use cases.

In the future, we could also add quick-fixes to the crate to be able to provide hints on the console and provide quick actions for the LSP.

This PR is branched of from #236 which should be merged first.

[codecov]

Codecov Report

Merging #239 into master will decrease coverage by 0.52%.
The diff coverage is 67.66%.

@@            Coverage Diff             @@
##           master     #239      +/-   ##
==========================================
- Coverage   79.10%   78.57%   -0.53%     
==========================================
  Files         201      210       +9     
  Lines       12807    12771      -36     
==========================================
- Hits        10131    10035      -96     
- Misses       2676     2736      +60     

Impacted Files	Coverage Δ
crates/mun_compiler/src/diagnostics.rs	100.00% <ø> (+6.30%)	⬆️
crates/mun_compiler/src/lib.rs	67.50% <ø> (ø)
crates/mun_diagnostics/src/hir/missing_fields.rs	0.00% <0.00%> (ø)
crates/mun_hir/src/diagnostics.rs	59.70% <ø> (-6.80%)	⬇️
crates/mun_hir/src/ty.rs	84.00% <0.00%> (-2.78%)	⬇️
crates/mun_language_server/src/diagnostics.rs	0.00% <0.00%> (ø)
crates/mun_language_server/src/main_loop.rs	23.55% <0.00%> (-1.33%)	⬇️
crates/mun_diagnostics/src/hir.rs	57.69% <57.69%> (ø)
crates/mun_hir/src/ty/infer.rs	70.94% <77.77%> (-0.04%)	⬇️
crates/mun_compiler/src/diagnostics_snippets.rs	84.00% <84.00%> (-7.94%)	⬇️
... and 20 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3a6b437...eb0da2c. Read the comment docs.