WIP fix for #4731: preserveWhitespace in SSR

[bwbroersma]

WIP fix for #4731.

Why this is still work in progress:

• the test works, but don't currently fail, because htmlEqual uses normalizeHtml which strips spaces & comments (same problem as Fix perserveComments on ssr (#4730) #4736), any advise?
  Update: solved by updating the testing code in #f2e0479
• trailing newlines are not generated in the _actual.html, but are in working with full samples, what am I missing?
• option in {#each}-loop still don't preserve whitespace (was looking at should_skip in src/compiler/compile/render_dom/wrappers/Text.ts)

Update: both open issues seem to be related to should_skip in src/compiler/compile/nodes/Text.ts, for some reason this check doesn't work (preserveWhitespace seems to be false):

		return parent_element.namespace
			|| elements_without_text.has(parent_element.name)
			&& (this.component.compile_options.preserveWhitespace
				|| this.component.component_options.preserveWhitespace);

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.