Fix character escapes in combobox options

[vidartf]

Fixes #2940. Independent of work in #2785 since these are limited to attribute values.

[jasongrout]

Instead of splicing sanitized strings together and using innerHTML, what do you think of constructing the option elements, adding them to a document fragment, then adding that at the end? Something like:

    const opts = this.model.get('options') as string[];
    const optionFragment = document.createDocumentFragment();
    opts.forEach(v => {
      const o = document.createElement('option');
      o.value = v;
      optionFragment.appendChild(o);
    })
    this.datalist.appendChild(optionFragment);

[vidartf]

When I originally wrote it, I found createElement loops to be less performant for large amounts of options (~10k+), but at the time I don't think I tried using document fragments. I've just ran some checks in chrome with 100k options and profiling and the performance seems to be at least same order of magnitude for the two, so I think your point about the code being much simpler should be the deciding factor here 👍

[jasongrout]

To be fair, I think we should be testing up to maybe 100 options. If someone is putting 10k options in, they have more serious problems and should probably be using a different filtering/selection strategy.

Edit: maybe up to 1000 options?

[jasongrout]

Thanks!