fix(relateditems): Move Select2 out of init.

If it wasn't already registered, it would register and scan the document now.
If there were previous relateditems already modifying the DOM structure
and placing pat-select2 classes to some items, the import here would try
to initialize them.
But those pat-select2 items were meant to be initialized via the
Patternslib API and not automatically and are missing some configuration
needed by select2 (query attribute...).
By moving the Select2 out of the init and importing it early fixes this
problem.

Note: This happened in plone.app.mosaic with module federation.
pat-select2 was already directly imported by the main Mockup bundle.
But since we didn't have a global pattern registry, the pattern was
re-initialized where it wouldn't have to.
Since the change in Patternslib 8.0.0 with a global pattern registry
this fix might become obsolete.

However, we should have an eye on dynamic pattern imports immediately
registering and scanning the docment and possibly prevent that in some
way.

See: Patternslib/Patterns#961

src/pat/relateditems/relateditems.js

@@ -5,6 +5,7 @@ import Base from "@patternslib/patternslib/src/core/base";
 import _t from "../../core/i18n-wrapper";
 import utils from "../../core/utils";
 import registry from "@patternslib/patternslib/src/core/registry";
+import Select2 from "../select2/select2";
 
 const KEY = {
     LEFT: 37,
@@ -503,7 +504,6 @@ export default Base.extend({
     },
 
     init: async function () {
-        const Select2 = (await import("../select2/select2")).default;
         (await import("bootstrap")).Dropdown;
         import("./relateditems.scss");