[BUGFIX] Apply proper url encoding to query params in form engine popups

With #101231 a missing URL encoding in FormEngine was triggered
which caused contents like "svg;disallowed=|irre-object-id" to be
added to bparams which got transformed into "svg&disallowed" in
some setups (ddev, most likely caused by the ddev-router-proxy).

This "change" causes the irre object id to be cut off from the
bparams in IREE file list element browser, which is why "select"
actions on file list elements were silently ignored.

Resolves: #101433
Related: #101231
Releases: main, 12.4, 11.5
Change-Id: I89dd53131f9ecb3b199bbcd2d1abf6be87f819da
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/80172
Tested-by: Benjamin Franzke <ben@bnf.dev>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: core-ci <typo3@b13.com>

typo3/sysext/backend/Resources/Public/JavaScript/FormEngine.js

@@ -114,7 +114,7 @@ define(['jquery',
   FormEngine.openPopupWindow = function(mode, params) {
     return Modal.advanced({
       type: Modal.types.iframe,
-      content: FormEngine.browserUrl + '&mode=' + mode + '&bparams=' + params,
+      content: FormEngine.browserUrl + '&' + (new URLSearchParams({mode: mode, bparams: params})).toString(),
       size: Modal.sizes.large
     });
   };