Issue #2912348 by maxocub, Jo Fitzgerald, masipila, heddn, phenaproxima: Handle entity_references related to Drupal 6 and 7 node translations with different IDs

Issue #2711099 by heddn, Jo Fitzgerald, edysmp, edgewl2, alexpott, Charlotte17, mikeryan, masipila, quietone, maxocub, phenaproxima: Categorize migrations according to their type

Issue #2914974 by quietone, rakesh.gectcr, maxocub, heddn, Jo Fitzgerald, Yogesh Pawar, masipila, phenaproxima, jhodgdon, Gábor Hojtsy, larowlan, neclimdul: Migrate UI - handle sources that do not need an upgrade

Issue #2876085 by heddn, maxocub, phenaproxima, Jo Fitzgerald, vasi, quietone, yoroy, masipila, larowlan, neclimdul, krystalcode, catch: Before upgrading, audit for potential ID conflicts

Issue #2917883 by quietone, TR, Jo Fitzgerald, masipila, phenaproxima: Rename 'migration_templates' directories in core modules to 'migrations'