chore(fuzz): AST generator to add ctx_limit to all functions

[aakoshh]

Description

Problem*

Preparation for #8484

Summary*

So far the ctx_limit: &mut u32 parameter has only been added to functions which called other functions. Now it will be part of the signature of all functions except main.

The PR also changes generation so only those Brillig functions which are called from ACIR get a _proxy variant, to reduce noise. We also stop generating ACIR functions if main is Brillig, because in code generated by the monomorphizer Brillig will only call other Brillig functions (apart from the #7279 problem). This is also to reduce noise.

Additional Context

In #8484 I want to pass function pointers as arguments in the generated AST.

Say we had program like this:

fn main() -> u32 {
  baz(bar)
}
fn foo() -> u32 {
  1 
}
fn bar() -> u32 {
  2 + foo()
}
fn baz(f: fn() -> u32) -> u32 {
  3 + f()
}

baz can be called with foo or bar.

According to the current rules, foo would be left alone, and bar would get a new ctx_limit parameter. But then baz could not take both functions as parameters any more: if we rewrite it into fn baz(f: fn(&mut u32) -> u32, ctx_limit: &mut u32) then it would only take bar, or we leave f alone and it can only take bar.

Instead, if we change all functions to take &mut u32, we can pass both.

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.