Make EditController edit_entity method always return an eid In cases the entity was to be created or copied, eid was None hence the method returned None despite the dosctring says the method should always return an eid. Now if the eid variable is None, it is assigned to the newly created entity eid. Closes #3593029.

[migration] Improve update of in-memory schema during 3.18 CWAttribute.defaultval change We weren't updating the schema properly so a bunch of structures still had the old rdef with 'String' as object. That caused failures to add new attributes later in the migration as their default value would be a Binary object but the schema would expect a String. Closes #3683640

[migration] always rebuild infered relation This was skipped for some bad reason (see 12ad88615a12 which introduced the change). Fix for #231956 in Yams is necessary to allow this cset: during a migration, we want to always reinfer relations while allowing explicit redefinition of an infered relation later. Else, we may run the migration with missing parts of the schema (the one that should have been infered). Closes #3685463.