fix: fixes a lot of llvm assertions

[baszalmstra]

Fixes a lot of LLVM assertions that were caused by invalid struct assignments due to casts being invalid. I introduced the Value::with_cast method to introduce an explicit cast.

Fixes these issues was a pain because the test just crashed. I had to insert a lot of print statements. I left some of them in (commented out) so in the future, it will be easier to fix these issues.

Closes #227

[codecov]

Codecov Report

Merging #233 into master will decrease coverage by 0.03%.
The diff coverage is 80.76%.

@@            Coverage Diff             @@
##           master     #233      +/-   ##
==========================================
- Coverage   81.14%   81.11%   -0.04%     
==========================================
  Files         182      182              
  Lines       11968    11996      +28     
==========================================
+ Hits         9711     9730      +19     
- Misses       2257     2266       +9     

Impacted Files	Coverage Δ
crates/mun_codegen/src/value/string.rs	21.42% <ø> (ø)
crates/mun_codegen_macros/src/lib.rs	0.00% <ø> (ø)
crates/mun_codegen/src/value/mod.rs	53.06% <50.00%> (-1.78%)	⬇️
crates/mun_codegen/src/code_gen/symbols.rs	94.73% <87.50%> (-0.04%)	⬇️
crates/mun_codegen/src/code_gen.rs	89.88% <100.00%> (+0.47%)	⬆️
crates/mun_codegen/src/db.rs	100.00% <100.00%> (ø)
crates/mun_codegen/src/ir/file_group.rs	100.00% <100.00%> (ø)
crates/mun_codegen/src/ir/type_table.rs	92.53% <100.00%> (+0.05%)	⬆️
crates/mun_codegen/src/value/array_value.rs	81.39% <100.00%> (+1.90%)	⬆️
crates/mun_codegen/src/value/global.rs	70.58% <100.00%> (ø)

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[Wodann]

Nice fixes. I have one remark and one question