perf(template-compiler): static-optimize `spellcheck`

[nolanlawson]

Details

Applies the static content optimization to elements with the spellcheck attribute.

We handle the spellcheck attribute in a special way. This seems due to a bug from years ago: https://github.com/salesforce/lwc/issues/1595

In any case, this PR makes it so static-optimized nodes render spellcheck in exactly the same way as non-static-optimized nodes. There are several tests to prove this.

Partially addresses #4280

Does this pull request introduce a breaking change?

• 😮‍💨 No, it does not introduce a breaking change.

Does this pull request introduce an observable change?

• 🤞 No, it does not introduce an observable change.