fix: stop inserting instructions after break and continue

[asterite]

Description

Problem

Resolves #8710
Resolves #8629
Resolves #8770

Summary

Now FunctionBuilder tracks whether the current block is closed. If so, no more instructions can be added to it. Then, on the codegen side, when we codegen break or continue we close the current block.

A few cases also need to check if the current block is closed to prevent trying to insert instructions via functions like insert_allocate and so on which check that a result is returned (but none is returned if the instruction is removed because the block is closed).

Finally, I realized that a break doesn't have a type (or, well, the type is a type variable) and that type was given to a block if it had an unconditional break. That's not correct. The correct thing to do would be to give the block the type "no return" or ! in Rust, but we don't have that. Instead, I chose unit as a type. At least it prevents code like 1 + { break; } to compile, and also makes #8629 give a better error.

To give a bit more detail on the last paragraph, the type of break should be ! by itself but, because we don't have that I chose (). However, in Rust this code:

let a = { break; 1 };

has a be i32, not !. That is, the type of a block is always the type of the last statement, regardless of it having a break/continue or not. I chose to do the same thing in Noir. It maybe leads to simpler error messages and more intuitive types.

Additional Context

Documentation

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 16ed24e	Previous: 89783b6	Ratio
rollup-merge	0.004 s	0.003 s	1.33

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Test Suite Duration'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: a8b5250	Previous: 89783b6	Ratio
test_report_AztecProtocol_aztec-packages_noir-projects_noir-protocol-circuits_crates_blob	53 s	43 s	1.23

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Compilation Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: b195fef	Previous: 58ce59e	Ratio
private-kernel-reset	9.074 s	7.35 s	1.23

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench