feat: Add comptime Interpreter (#4821)

# Description

## Problem\*

Resolves #4587

## Summary\*

Implements an interpreter to interpret Noir functions at compile-time.
This is intended to be used in the future for evaluation of `comptime`
items for metaprogramming, although there is currently no way to trigger
this interpreter in user code.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: Maxim Vezenov <mvezenov@gmail.com>

Cargo.toml

@@ -132,6 +132,7 @@ tempfile = "3.6.0"
 jsonrpc = { version = "0.16.0", features = ["minreq_http"] }
 flate2 = "1.0.24"
 
+im = { version = "15.1", features = ["serde"] }
 tracing = "0.1.40"
 tracing-web = "0.1.3"
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }

compiler/noirc_evaluator/Cargo.toml

@@ -15,7 +15,7 @@ fxhash.workspace = true
 iter-extended.workspace = true
 thiserror.workspace = true
 num-bigint = "0.4"
-im = { version = "15.1", features = ["serde"] }
+im.workspace = true
 serde.workspace = true
 tracing.workspace = true
-chrono = "0.4.37"
+chrono = "0.4.37"

compiler/noirc_frontend/Cargo.toml

@@ -17,6 +17,7 @@ iter-extended.workspace = true
 chumsky.workspace = true
 thiserror.workspace = true
 smol_str.workspace = true
+im.workspace = true
 serde_json.workspace = true
 serde.workspace = true
 rustc-hash = "1.1.0"

compiler/noirc_frontend/src/ast/expression.rs

@@ -387,6 +387,9 @@ pub struct FunctionDefinition {
     /// True if this function was defined with the 'unconstrained' keyword
     pub is_unconstrained: bool,
 
+    /// True if this function was defined with the 'comptime' keyword
+    pub is_comptime: bool,
+
     /// Indicate if this function was defined with the 'pub' keyword
     pub visibility: ItemVisibility,
 
@@ -679,10 +682,12 @@ impl FunctionDefinition {
                 span: ident.span().merge(unresolved_type.span.unwrap()),
             })
             .collect();
+
         FunctionDefinition {
             name: name.clone(),
             attributes: Attributes::empty(),
             is_unconstrained: false,
+            is_comptime: false,
             visibility: ItemVisibility::Private,
             generics: generics.clone(),
             parameters: p,