`positionMenu` will cause JS promise error when use `multiword` and promise for `provide`

[wxiaoguang]

Stacktrace:

Uncaught (in promise) IndexSizeError: Failed to execute 'setStart' on 'Range': The offset 28 is larger than the node's length (27).
    at #createCloneRange
    at InputRange.getBoundingClientRect
    at TextExpander.positionMenu
    at TextExpander.activate
    at TextExpander.onInput

It seems that 2 bugs are related:

1. when provide a promise, after await Promise.all(providers), the textarea's content might have changed.

But activate and positionMenu still use old (outdated) match, then the position in const caretRect = new InputRange(this.input, position).getBoundingClientRect(); is invalid.

2. the query will return incorrect position for "multiword" when the last "key" is removed.

---

To reproduce:

<text-expander multiword="#">...</>

provide(async () => {
    await sleep(Math.random() * 1000); 
    return {matched: true .....};
});

Then use the textarea value:

close #20
close #20 
close #20

And delete the chars in the last line from the end, when the # in the last line is deleted, the JS error occurs. It's quite strange that it must have 3 lines to reproduce the bug.