Execution stack & promises (#2107)

This PR overrides #1923. It also removes the `queues` dependency added there, and rebases it to the latest `main` branch state.

It adds the following:

- A job queue (in `Context`)
- The constructor [`Promise`](https://tc39.es/ecma262/#sec-promise-executor)
- [`Promise.race`](https://tc39.es/ecma262/#sec-promise.race)
- [`Promise.reject`](https://tc39.es/ecma262/#sec-promise.reject)
- [`Promise.resolve`](https://tc39.es/ecma262/#sec-promise.resolve)
- [`get Promise [ @@species ]`](https://tc39.es/ecma262/#sec-get-promise-@@species)
- [`Promise.prototype [ @@toStringTag ]`](https://tc39.es/ecma262/#sec-promise.prototype-@@tostringtag)
- [`Promise.prototype.then`](https://tc39.es/ecma262/#sec-promise.prototype.then)
- [`Promise.prototype.finally`](https://tc39.es/ecma262/#sec-promise.prototype.finally)
- [`Promise.prototype.catch`](https://tc39.es/ecma262/#sec-promise.prototype.catch)
- The additional needed infrastructure
  - [`PerformPromiseThen ( promise, onFulfilled, onRejected [ , resultCapability ] )`](https://tc39.es/ecma262/#sec-performpromisethen)
  - [`TriggerPromiseReactions ( reactions, argument )`](https://tc39.es/ecma262/#sec-triggerpromisereactions)
  - [`PerformPromiseRace ( iteratorRecord, constructor, resultCapability, promiseResolve )`](https://tc39.es/ecma262/#sec-performpromiserace)
  - [`RejectPromise ( promise, reason )`](https://tc39.es/ecma262/#sec-rejectpromise)
  - [`FulfillPromise ( promise, value )`](https://tc39.es/ecma262/#sec-fulfillpromise)
  - [`IfAbruptRejectPromise ( value, capability )`](https://tc39.es/ecma262/#sec-ifabruptrejectpromise)
  - [`CreateResolvingFunctions ( promise )`](https://tc39.es/ecma262/#sec-createresolvingfunctions)
  - [`NewPromiseCapability ( C )`](https://tc39.es/ecma262/#sec-newpromisecapability)
  - [`NewPromiseReactionJob ( reaction, argument )`](https://tc39.es/ecma262/#sec-newpromisereactionjob)
  - [`NewPromiseResolveThenableJob ( promiseToResolve, thenable, then )`](https://tc39.es/ecma262/#sec-newpromiseresolvethenablejob)
  - [`PromiseResolve ( C, x )`](https://tc39.es/ecma262/#sec-promise-resolve)
- A test case showcasing the run-to-completion semantics.

An example program that shows the control flow with this addition is:
```javascript
new Promise((res, rej) => {
  console.log("A");
  res(undefined);
}).then((_) => console.log("B"));
console.log("C");
```
Which would output:
```
A
C
B
```

boa_engine/src/builtins/iterable/mod.rs

@@ -202,19 +202,26 @@ pub struct IteratorResult {
 }
 
 impl IteratorResult {
-    /// Get `done` property of iterator result object.
+    /// `IteratorComplete ( iterResult )`
+    ///
+    /// The abstract operation `IteratorComplete` takes argument `iterResult` (an `Object`) and
+    /// returns either a normal completion containing a `Boolean` or a throw completion.
     ///
     /// More information:
     ///  - [ECMA reference][spec]
     ///
-    /// [spec]: https://tc39.es/ecma262/#sec-iteratorclose
+    /// [spec]: https://tc39.es/ecma262/#sec-iteratorcomplete
     #[inline]
     pub fn complete(&self, context: &mut Context) -> JsResult<bool> {
         // 1. Return ToBoolean(? Get(iterResult, "done")).
         Ok(self.object.get("done", context)?.to_boolean())
     }
 
-    /// Get `value` property of iterator result object.
+    /// `IteratorValue ( iterResult )`
+    ///
+    /// The abstract operation `IteratorValue` takes argument `iterResult` (an `Object`) and
+    /// returns either a normal completion containing an ECMAScript language value or a throw
+    /// completion.
     ///
     /// More information:
     ///  - [ECMA reference][spec]
@@ -226,13 +233,16 @@ impl IteratorResult {
         self.object.get("value", context)
     }
 }
+
+/// Iterator Record
+///
 /// An Iterator Record is a Record value used to encapsulate an
-/// `Iterator` or `AsyncIterator` along with the next method.
+/// `Iterator` or `AsyncIterator` along with the `next` method.
 ///
 /// More information:
 ///  - [ECMA reference][spec]
 ///
-/// [spec]:https://tc39.es/ecma262/#table-iterator-record-fields
+/// [spec]: https://tc39.es/ecma262/#sec-iterator-records
 #[derive(Debug)]
 pub struct IteratorRecord {
     /// `[[Iterator]]`
@@ -265,7 +275,11 @@ impl IteratorRecord {
         &self.next_function
     }
 
-    /// Get the next value in the iterator
+    /// `IteratorNext ( iteratorRecord [ , value ] )`
+    ///
+    /// The abstract operation `IteratorNext` takes argument `iteratorRecord` (an `Iterator`
+    /// Record) and optional argument `value` (an ECMAScript language value) and returns either a
+    /// normal completion containing an `Object` or a throw completion.
     ///
     /// More information:
     ///  - [ECMA reference][spec]
@@ -298,7 +312,18 @@ impl IteratorRecord {
         }
     }
 
-    #[inline]
+    /// `IteratorStep ( iteratorRecord )`
+    ///
+    /// The abstract operation `IteratorStep` takes argument `iteratorRecord` (an `Iterator`
+    /// Record) and returns either a normal completion containing either an `Object` or `false`, or
+    /// a throw completion. It requests the next value from `iteratorRecord.[[Iterator]]` by
+    /// calling `iteratorRecord.[[NextMethod]]` and returns either `false` indicating that the
+    /// iterator has reached its end or the `IteratorResult` object if a next value is available.
+    ///
+    /// More information:
+    ///  - [ECMA reference][spec]
+    ///
+    /// [spec]: https://tc39.es/ecma262/#sec-iteratorstep
     pub(crate) fn step(&self, context: &mut Context) -> JsResult<Option<IteratorResult>> {
         let _timer = Profiler::global().start_event("IteratorRecord::step", "iterator");
 
@@ -317,7 +342,12 @@ impl IteratorRecord {
         Ok(Some(result))
     }
 
-    /// Cleanup the iterator
+    /// `IteratorClose ( iteratorRecord, completion )`
+    ///
+    /// The abstract operation `IteratorClose` takes arguments `iteratorRecord` (an
+    /// [Iterator Record][Self]) and `completion` (a Completion Record) and returns a Completion
+    /// Record. It is used to notify an iterator that it should perform any actions it would
+    /// normally perform when it has reached its completed state.
     ///
     /// More information:
     ///  - [ECMA reference][spec]

boa_engine/src/builtins/mod.rs

@@ -20,6 +20,7 @@ pub mod math;
 pub mod nan;
 pub mod number;
 pub mod object;
+pub mod promise;
 pub mod proxy;
 pub mod reflect;
 pub mod regexp;
@@ -57,6 +58,7 @@ pub(crate) use self::{
     number::Number,
     object::for_in_iterator::ForInIterator,
     object::Object as BuiltInObjectObject,
+    promise::Promise,
     proxy::Proxy,
     reflect::Reflect,
     regexp::RegExp,
@@ -182,7 +184,8 @@ pub fn init(context: &mut Context) {
         AggregateError,
         Reflect,
         Generator,
-        GeneratorFunction
+        GeneratorFunction,
+        Promise
     };
 
     #[cfg(feature = "intl")]