Fix: Tie more elements from DOM snapshot back to original source

[antross]

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Short description of the change(s)

Ref #1956

Also fix some cases where use of the snapshot vs. original document were
inconsistent between connectors (except connector-local which needs to
be different).

Notable changes:

• All connectors now use parser-html to obtain an original source document
  • Should we consider making parser-html fully built-in since HTML handling is so special?
• Snapshots are created with a reference to the original source document for locations
  • This means we no longer use locations from the snapshot itself (I turned off locations for snapshots to ensure this)
  • A new findOriginalElement helper was added to take an element from the snapshot and build a selector (plus filter function) to identify the same element in the original source (if one exists).
• If an element was dynamically created, we no longer try to produce a location for it.
  • This avoids producing invalid locations that don't point anywhere in actual source.
  • In future updates some contexts (e.g. the browser extension) may link to the actual element reference instead in these cases.

Marking as "Draft" while I wait for test results which may require some updates.

[molant]

All connectors now use parser-html to obtain an original source document

I only see import for type definitions and nothing else. Can you please point me to the right place?

[molant]

@antross do you want to do more changes or is this ready to be merged?

[antross]

@molant I made one last tweak to fix the issue I discussed earlier where an element with an ID or URL could end up falling back if no match is found and matching (incorrectly) on content. Now this should be good to merge!