The translation of sections edited by VE are saved. They need to be restored against its source sections when translation is resumed.
[x] The basic algorithm is to match against the section identifiers.
 If source article changed heavily, we need to use a better algorithm to identify source sections even if it changed. (Showing a warning to the user is part of a separate ticket, T168287)
[x] Support CX1 translations by relying on parsoid generated ids
[x] Restoring translations against source sections even if those sections moved around.
 And fallback to original source revision if source article changed beyond restoring a saved translation.
[x] Status message about fetching the saved translation should be shown to translator
[x] Status message about restoring the fetched translation should be shown to translator
[x] Restore the modified translation title if any
With the recent regressions (T187683), this ticket requires to re-evaluate the checked boxes above, and completing the remaining ones.