evalCode(type=module) throws instead of returning rejected promise

[justjake]

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Fixes #160

New versions of quickjs library return Promise<void> when evaluating a module.

Our wrapper code unwrapped this implicit promise if it's resolved and return the module exports, and replace a pending promise with pending Promise<ModuleExports>.

However, our code passed through the rejected promise value as a success result back to the caller, who probably isn't expecting a promise.

With this PR, we consider the sync rejected module evaluation promise as an error, restoring the behavior of errors thrown during evaluation.

Also: context.dump(val) now inspects promises