feat(experimental): Implement macro calls & splicing into Expr values

[jfecher]

Description

Problem*

Resolves #4591

Summary*

Implements macro calls foo!() and splicing via the $ operator of Expr values into quote expressions.

comptime fn my_macro(x: Field, y: Field) -> Expr {
    quote { $x + $y + x + y }
}

fn main(x: Field, y: pub Field) {
    let result = my_macro!(1, 2);
    assert_eq(result, 1 + 2 + x + y);
}

Additional Context

This feature is elaborator-only and does not work with the resolver / type checker. I've yet to add the integration test that pairs with this as a result since I'd have to add a check to the build step to exclude it from any runs without --use-elaborator. I'll add this later but the PR should be ready for review at least now.

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.

[jfecher]

This PR looks deceptively large but the largest chunks are repetitive bits:

• Two new AST passes in:
  • compiler/noirc_frontend/src/elaborator/unquote.rs: Finds Unquote Ast nodes within Quote Ast nodes, resolves the unquoted value, inserts that into a context for the unquote node, and replaces them with another node to mark the position of the unquote node.
  • compiler/noirc_frontend/src/hir/comptime/interpreter/unquote.rs: Finds the unquote markers created by the previous pass and replaces them with the value evaluated by the interpreter.
  • Together this is how the interpreter splices code into Quote nodes. Most of the code here is just recurring on the Ast.

The other bulk of this PR are parser changes which I've broken out separately into #5229