Adds break expressions

[baszalmstra]

This PR adds the break expression to Mun. It allows breaking from loops and enables loops to have return types different from never.

The following code should work properly.

fn fibonacci(n:int):int {
    let a = 0;
    let b = 1;
    let i = 1;
    loop {
        if i > n {
            break a;
        }
        let sum = a + b;
        a = b;
        b = sum;
        i += 1;
    }
}

Here the loop should get the int type instead of the never type due to the break a statement.

• Implement parsing of break expressions.
• Implement proper type inferencing and diagnostics
  • Do not allow break expression outside loops
  • Multiple break expressions must have the same type
• Implement code generation for the break statement

Depends on #60

[baszalmstra]

Break expression

[codecov]

Codecov Report

Merging #62 into master will increase coverage by 0.25%.
The diff coverage is 85%.

@@            Coverage Diff             @@
##           master      #62      +/-   ##
==========================================
+ Coverage   71.08%   71.34%   +0.25%     
==========================================
  Files         106      106              
  Lines        6928     7073     +145     
==========================================
+ Hits         4925     5046     +121     
- Misses       2003     2027      +24

Impacted Files	Coverage Δ
crates/mun_syntax/src/parsing/token_set.rs	68.18% <ø> (ø)	⬆️
crates/mun_codegen/src/ir/body.rs	85.5% <100%> (+1.3%)	⬆️
crates/mun_syntax/src/syntax_kind/generated.rs	79.34% <100%> (+0.11%)	⬆️
crates/mun_runtime/src/test.rs	95.76% <100%> (+0.26%)	⬆️
crates/mun_syntax/src/tests/parser.rs	98.14% <100%> (+0.1%)	⬆️
crates/mun_hir/src/ty/tests.rs	95.91% <100%> (+0.12%)	⬆️
crates/mun_codegen/src/test.rs	100% <100%> (ø)	⬆️
crates/mun_hir/src/diagnostics.rs	16.21% <20%> (+0.27%)	⬆️
crates/mun_syntax/src/ast/generated.rs	56.17% <66.66%> (+0.3%)	⬆️
crates/mun_hir/src/expr.rs	76.05% <90%> (+0.33%)	⬆️
... and 2 more

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