[pkg] prepare 3.18.4

[web] Disable 'concat-resources' by default (closes #3670503) It makes debugging harder and it can actually *break* working JS or CSS files. This is the first step towards complete removal.

[testlib] Drop override of assertItemsEqual method The override is not compatible with underlying (standard) method because it builds sets and rely on eid. Closes #3641111.

[rewrite] Fix crash when the main variable doesn't appear in the snippet's vargraph Also, the added test discover another bug once the first has been fixed (erroneous argument given to .rewrite recursive call). Closes #3661918

[ext/rest] Catch SystemExit raised by docutils docutils publisher may raise SystemExit which is not caught by Exception. Closes #3648763.

[entity] User-defined relation to skip for copy has precedence Otherwise permission problems can occur on rtypes not yet skipped Closes #3653459

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.

Backout "[web/navigation] use add_onload instead of inline javascript href" This reverts changeset 170e1437948d, for at least two reasons: the PageNavigationSelect component was not updated for the new type of navigation links, and external cubes defining View.page_navigation_url exist in the wild and also got broken navigation links. This reopens #3501626 and closes #3677945.