Subset of "Don't prevent component deletion" MR

Co-authored-by: Dave Long 24510-longwave@users.noreply.drupalcode.org (cherry picked from commit 1eccc440)

Closes (?) #3519168

Contents of this MR are the result of XB team daily scrum. Attendees agreed that the size of the MR is getting out of hand, so this attempts to get some of the work merged in, while "data loss" related aspects of the code (Fallback source plugin mechanism) is still being discussed.