Find in Files Improvements (Part 3: Auto-update)

Here comes the part 3 of the Find in Files improvements PR #3151.

This PR updates the find in files results on documents changes. It listens the change event on the current document and searches over the modified lines, adding the new results or deleting the old ones. It also updates the line numbers of the rest of the results, it can remove a complete file from the results when there aren't any anymore or add a new one.