chore(fuzz): Refactor logging in the AST fuzzer

[aakoshh]

Description

Problem*

Follow up for the issue @vezenovm encountered in #9882 (comment)

Summary*

• Changes the way we can tell the AST fuzzer to log the generated artifacts to be triggered by the RUST_LOG=debug env var, which now causes everything to be printed as logs from the arb methods.
• Removes the NOIR_AST_FUZZER_SHOW_AST option, which was used to print the AST before trying to convert it into SSA, used mainly for debug if the compilation panicked. Instead if NOIR_AST_FUZZER_SEED is present, it will automatically print the AST iff there is an error during compilation.
• Renames create_ssa_or_die to compile_into_circuit_or_die, because some passes actually create Ssa, while the SsaProgramArtifact doesn't actually have the Ssa in it, which is a bit confusing.
• Omits the Brillig bytecode from the output when there is an error, as this was always just an unreadable wall of text.

Additional Context

An example of the new output:

❯ RUST_LOG=debug NOIR_AST_FUZZER_SEED=0xe6851ab700100000 cargo test -q -p noir_ast_fuzzer_fuzz pass_vs_prev
running 1 test
[2025-09-17T09:42:14Z DEBUG noir_ast_fuzzer::compare::logging] AST:
    global G_A: [[str<1>; 4]; 4] = [["P", "T", "C", "Q"], ["Q", "N", "O", "Q"], ["A", "B", "T", "H"], ["V", "X", "C", "U"]];
    global G_B: [str<1>; 4] = ["L", "K", "G", "J"];
    global G_C: [[str<1>; 4]; 4] = [["G", "Y", "A", "V"], ["Z", "E", "Z", "I"], ["X", "B", "H", "A"], ["S", "G", "S", "Y"]];
    unconstrained fn main() -> pub [(bool, str<1>, str<1>, str<1>); 1] {
        let mut ctx_limit: u32 = 25_u32;
        let mut a = G_C[(if true {
            3859550138_u32
        } else {
            if false {
                2150811138_u32
            } else {
                if true {
                    if false {
                        1330515451_u32
                    } else {
                        2516186332_u32
                    }
                } else {
                    2760297220_u32
                }
            }
        } % 4_u32)];
        for idx_b in 1908093938_i32 .. 1908093946_i32 {
            break;
        };
        [(false, a[(3324712353_u32 % 4_u32)], a[2_u32], a[2_u32])]
    }
    
    
targets::pass_vs_prev::tests::fuzz_with_arbtest --- FAILED

failures:

---- targets::pass_vs_prev::tests::fuzz_with_arbtest stdout ----

thread 'targets::pass_vs_prev::tests::fuzz_with_arbtest' panicked at compiler/noirc_evaluator/src/ssa/opt/mem2reg.rs:454:46:
index out of bounds: the len is 23 but the index is 37
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

arbtest failed!
    Seed: 0xe6851ab700100000




failures:
    targets::pass_vs_prev::tests::fuzz_with_arbtest

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 5 filtered out; finished in 0.03s

error: test failed, to rerun pass `-p noir_ast_fuzzer_fuzz --lib`

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.