Spec compliance: finally block of sync generator should not execute if used in async loop while yielding rejected promise

## Bug Report

**Current Behavior**
According to the spec the code
```js
function* generator() {
try {
yield Promise.resolve(2)
yield Promise.reject(new Error(3))
} finally {
print("finally")
}
}

// 1)
async function () {
for (const x of generator()) consume(await x)
}

// 2)
async function () {
for await (const x of generator()) consume(x)
}

// 3)
async function* () {
yield* generator()
}
```
should print "finally" only in the 1) case.

In the cases 2) and 3) finally block of the generator should not be executed.

Node@10 and above, current firefox and chromium have spec compliant behavior.

Babel when transpiling not node@8 has wrong behavior according to spec.

Now a lot of code is transpiled by people to the node@8 js version, and so async generators are transpiled by babel in the non-spec complained way. When the node@8 becomes obsolete and that code will be transpiled to node@10 then it can start to behave in a different way.

I suggest this should be fixed in the spec, not in the babel, though I think it's worth to make spec-compliance in some way.

Refs:
https://github.com/tc39/ecma262/issues/1849
https://bugzilla.mozilla.org/show_bug.cgi?id=1610315#c1

Start by reproducing the three generator examples in the issue and compare their behavior with Node, Firefox, Chromium, and Babel targeting Node 8. Read the linked tc39/ecma262 issue and Mozilla discussion to determine whether the required change belongs in the spec or Babel; done requires an agreed spec-compliant resolution.

Written by the indexing model from the issue text.