tech(pat-modal): lazify pattern, split registration from implementation

Split the ~1000-line pat-modal implementation out of the every-page
eager patterns chunk. modal.js becomes a thin registration module that
loads modal--implementation.js on first .pat-plone-modal match; the
implementation grafts onto the instance from the prototype, since
imperative callers still do `new Modal()`.

jquery-form ($.fn.ajaxSubmit) moves from a top-level import to a lazy
`await import("jquery-form")` at its single call site in
handleFormAction, so it no longer loads on every page.

Imperative importers are repointed at modal--implementation:
controlpanels (registry / dexterity-types-listing / contentrule-elements)
and recurrence load it as part of their own lazy implementation chunks;
manageportlets is registered eagerly, so it loads the impl on demand
inside showEditPortlet. Side-effect registration imports (patterns.js,
tinymce links, structure actionmenu) keep pointing at the thin module.

Depends on the pat-recurrence lazification: recurrence is eagerly
registered, so its Modal import must live in recurrence--implementation
(a lazy chunk) for the modal body to actually leave the eager bundle.
Merge after the pat-recurrence PR.

Author: MrTango

src/pat/controlpanels/contentrule-elements--implementation.js

@@ -1,5 +1,5 @@
 import $ from "jquery";
-import Modal from "../modal/modal";
+import Modal from "../modal/modal--implementation";
 
 export default class Contentrules {
     constructor(el) {

src/pat/controlpanels/dexterity-types-listing--implementation.js

@@ -1,5 +1,5 @@
 import $ from "jquery";
-import Modal from "../modal/modal";
+import Modal from "../modal/modal--implementation";
 
 export default class DexterityTypesListing {
     constructor(el) {

src/pat/controlpanels/registry--implementation.js

@@ -1,6 +1,6 @@
 import $ from "jquery";
 import utils from "../../core/utils";
-import Modal from "../modal/modal";
+import Modal from "../modal/modal--implementation";
 
 export default class ConfigRegistry {
     constructor(el) {

src/pat/manageportlets/manageportlets.js

@@ -1,5 +1,4 @@
 import $ from "jquery";
-import Modal from "../modal/modal";
 import Base from "@patternslib/patternslib/src/core/base";
 import logger from "@patternslib/patternslib/src/core/logging";
 import utils from "../../core/utils";
@@ -109,8 +108,11 @@ export default Base.extend({
             $message.fadeTo(500, 0.6);
         }, 3000);
     },
-    showEditPortlet: function (url) {
+    showEditPortlet: async function (url) {
         log.info("show edit portlet in modal");
+        // manageportlets is registered eagerly, so it loads the modal
+        // implementation on demand to keep it out of the eager bundle.
+        const Modal = (await import("../modal/modal--implementation")).default;
         var that = this;
         var $a = $("<a/>");
         $("body").append($a);