Odd behavior with <options> and keyed each

[zzolo]

REPL example:
https://svelte.technology/repl?version=2.13.2&gist=008feaa0cf6115dc506175b38dff9583

If you used a key in a each block for <option>s in a <select>, and then dynamically change the set of options, the behavior is odd. I am not sure I can describe. I am not 100% it's not acting like it is intended either.

[Conduitry]

Closing this in favor of #1764, which has more discussion.