Update `ExperienceBuilderController` to pass current user's XB high-level permissions to the client

Overview

The following permissions determine access to high-level features in the XB UI, and will allow the UI to perform a simple if (boolean) { show(); }-style check:

1. Administer Page Template (for PageRegion config entities, which together make up the "page template") → show the Move to global region option in context menus … or not
2. Administer Sections (for Pattern config entities) → show "Create section" in context menus … or not (⚠️ list of sections to use is always available!)
3. Administer Code Components (for JavaScriptComponent and AssetLibrary config entities) → show "Add component" and "Code" in sidebar + request /xb/api/js_component … or not

Partially blocked on #3508694: Permissions for XB config entity types, because Pattern doesn't yet have the appropriate permission.

Proposed resolution

diff --git a/src/Controller/ExperienceBuilderController.php b/src/Controller/ExperienceBuilderController.php
index 94dfed312..f1878b80f 100644
@@ -110,6 +111,11 @@ HTML;
             'jsFooter' => $this->assetRenderer->renderJsFooterAssets($preview_assets),
           ],
           'xbModulePath' => $xb_module_path,
+          'permissions' => [
+            'globalRegion' => $this->currentUser->hasPermission(PageRegion::ADMIN_PERMISSION),
+            'sections' => $this->currentUser->hasPermission(Pattern::ADMIN_PERMISSION),
+            'codeComponents' => $this->currentUser->hasPermission(JavaScriptComponent::ADMIN_PERMISSION),
+          ],
         ],
       ],
       // Note: the tokens here are under our control, and this accepts no user

User interface changes

None; that's for #3516641: Make the XB UI show only UI elements/operations available to the current user and related issues to tackle.