feat: add Param type to Function

[baszalmstra]

Adds the Param type to Function which gives access to the source of the parameter.

I also fixed a few deprecation warnings.

[Wodann]

The changes look good to me, but there is a CI failure due to a deprecated member variable being used.

[baszalmstra]

The changes look good to me, but there is a CI failure due to a deprecated member variable being used.

I think I fixed it by pinning lsp-types for now.

[codecov]

Codecov Report

Attention: Patch coverage is 67.01031% with 32 lines in your changes are missing coverage. Please review.

Project coverage is 87.40%. Comparing base (b68a952) to head (9c8de22).

Files	Patch %	Lines
crates/mun_hir/src/code_model/function.rs	0.00%	30 Missing ⚠️
crates/mun_hir/src/item_tree.rs	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #559      +/-   ##
==========================================
+ Coverage   87.30%   87.40%   +0.10%     
==========================================
  Files         276      276              
  Lines       32035    32157     +122     
==========================================
+ Hits        27968    28108     +140     
+ Misses       4067     4049      -18     

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