feat: assoc method completion

[baszalmstra]

This PR refactors how we analyze the context of completions and adds completion of associated methods.

There is some unused code in this PR which I need for adding more completions (like methods and use statements). I didnt add them to this PR yet to make sure it doesnt grow to big.

[codecov]

Codecov Report

Attention: Patch coverage is 87.86885% with 37 lines in your changes missing coverage. Please review.

Project coverage is 87.88%. Comparing base (3d70e0e) to head (589f672).

Files with missing lines	Patch %	Lines
...language_server/src/completion/context/analysis.rs	82.02%	16 Missing ⚠️
crates/mun_hir/src/source_analyzer.rs	65.62%	11 Missing ⚠️
crates/mun_hir/src/semantics.rs	50.00%	3 Missing ⚠️
crates/mun_language_server/src/completion/item.rs	0.00%	2 Missing ⚠️
crates/mun_language_server/src/to_lsp.rs	50.00%	2 Missing ⚠️
crates/mun_language_server/src/completion/expr.rs	98.27%	1 Missing ⚠️
...tes/mun_language_server/src/completion/name_ref.rs	93.33%	1 Missing ⚠️
crates/mun_language_server/src/file_structure.rs	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #578      +/-   ##
==========================================
+ Coverage   87.61%   87.88%   +0.27%     
==========================================
  Files         271      273       +2     
  Lines       31861    32080     +219     
==========================================
+ Hits        27914    28193     +279     
+ Misses       3947     3887      -60     

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[Wodann]

Overall LGTM. One question

[baszalmstra]

I downgraded the runners from ubuntu-latest to ubuntu-22.04 because llvm 14 is not available for later versions of ubuntu from the official repository.