bump: rust 1.49

[baszalmstra]

Bumps rust to the latest 1.49 and fixes clippy warnings

[codecov]

Codecov Report

Merging #291 (c8ac6a7) into master (e410bc5) will decrease coverage by 0.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #291      +/-   ##
==========================================
- Coverage   79.64%   79.51%   -0.14%     
==========================================
  Files         228      228              
  Lines       13478    13425      -53     
==========================================
- Hits        10735    10675      -60     
- Misses       2743     2750       +7     

Impacted Files	Coverage Δ
crates/mun_codegen/src/code_gen/symbols.rs	94.69% <100.00%> (ø)
crates/mun_hir/src/expr/scope.rs	93.44% <100.00%> (ø)
crates/mun_lld/src/lib.rs	86.66% <100.00%> (ø)
crates/mun_syntax/src/parsing/lexer/classes.rs	100.00% <100.00%> (ø)
crates/mun_hir/src/path.rs	68.75% <0.00%> (-3.13%)	⬇️
crates/mun_syntax/src/parsing/text_tree_sink.rs	88.57% <0.00%> (-2.86%)	⬇️
crates/mun_hir/src/expr/validator.rs	94.87% <0.00%> (-2.57%)	⬇️
crates/mun_runtime/src/assembly.rs	68.08% <0.00%> (-2.13%)	⬇️
crates/mun_abi/src/type_info.rs	81.39% <0.00%> (-1.69%)	⬇️
...mun_hir/src/expr/validator/uninitialized_access.rs	75.00% <0.00%> (-1.52%)	⬇️
... and 31 more

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