Editorial: add a note about synchronicity of SyntheticModule Evaluate

[legendecas]

It is not clear if a Synthetic Module's [[EvaluationSteps]] should be sync or not by reading the steps in Synthetic Module's Evaluate algorithm solely.

The synchronicity of a Synthetic Module's Evaluate steps is asserted in EvaluateModuleSync.

Add a note at Synthetic Module Evaluate abstract operation about the synchronicity.

[nicolo-ribaudo]

That the returned promise here is always settled is obvious, because the second-to-last line calls Call(_pc_.[[Resolve]], *undefined*, « *undefined* »).

However, what we should do is enforce that all non-Cyclic module records must always return a settled promise. I suggest doing it in the Evaluate description at https://tc39.es/ecma262/#table-abstract-methods-of-module-records, so that if hosts provide their own module types they must also follow that requirement.

[legendecas]

Thanks for the suggestion, updated!

[nicolo-ribaudo]

Suggested change

	<p>A non Cyclic Module Record must always returns a settled promise. This is asserted in InnerModuleEvaluation, and a non Cyclic Module Record is evaluated with EvaluateModuleSync.</p>
	<p>A non Cyclic Module Record must always returns a settled promise.</p>

From a host point view the only thing that matters is what they have to do, and not what algorithms would break if they don't. Similarly, for "Link must have completed successfully prior to invoking this method" we do not say that that's asserted in step 2 of Evaluate.

(and if we do need to link, we should do it so through <emu-xref> so that it stays up to date)