shadow-to-light should support lwc:dom=manual transformations for static stylesheets

[nolanlawson]

We do some special transformations for lwc:dom=manual. However, these currently rely on detecting lwc:dom=manual in a component.html file and then applying it to the associated component.css file.

In the case of static stylesheets, the component JS could do something like:

import aHtml from './a.html'
import bHtml from './b.html'
import sheet from './sheet.css'

export default class extends LightningElement {
  static stylesheets = [sheet]

  render() {
    return someCondition ? aHtml : bHtml
  }
}

In this case, both a.html and b.html could contain their own lwc:dom=manual blocks, and sheet.css would ideally be able to support those.