[ajax] use a custom tag to handle dynamically loaded js Using <pre class="script"> makes it trivial for a malicious user to inject arbitrary javascript into a html or rest text element (because it looks innocent to the html sanitizer). Using a custom tag we can be sure that it actually comes from our code and not from untrusted user data. IE ignores custom tags, though, so we put it in its own namespace. https://extranet.logilab.fr/1530578

[dataimport] fix comment

[hooks/security, devtools/fill] silence yams 0.38.0 warnings

Drop 3.13 incomplete backward compat in edit controller. It is very old and broken (there is another non-backward-copmpatible usage of `_cw_entity_fields`), better to remove it instead of fixing. Closes #3515223.