[BUGFIX] Use IconAPI where applicable to fetch Core icons (#451)

This change makes use of the IconViewHelper to fetch icons delivered
with TYPO3 via its official API.

Where not applicable, the icon configuration is fetched instead to
obtain the icon's source path.

Fixes: #450

Author: andreaskienast

Classes/Hook/FrontendEditingInitializationHook.php

@@ -468,9 +468,10 @@ protected function getPageTreeStructure(): array
             }
         }
 
+        $appsPagetreeRootIcon = $this->iconRegistry->getIconConfigurationByIdentifier('apps-pagetree-root');
         return [
             'name' => $GLOBALS['TYPO3_CONF_VARS']['SYS']['sitename'],
-            'icon' => $this->getAbsolutePath('EXT:core/Resources/Public/Icons/T3Icons/apps/apps-pagetree-root.svg'),
+            'icon' => $this->getAbsolutePath($appsPagetreeRootIcon['options']['source']),
             'children' => $children
         ];
     }

Resources/Private/Partials/LeftBar.html

@@ -13,33 +13,33 @@
 			<f:if condition="{pageNewUrl}">
 				<li>
 					<button type="#" class="btn t3-frontend-editing__page-new" data-url="{pageNewUrl}">
-						<fe:svg source="EXT:core/Resources/Public/Icons/T3Icons/actions/actions-page-new.svg"/>
+						<core:icon identifier="actions-page-new"/>
 					</button>
 				</li>
 			</f:if>
 			<f:if condition="{pageEditUrl}">
 				<li>
 					<button type="#" class="btn t3-frontend-editing__page-edit" data-url="{pageEditUrl}">
-						<fe:svg source="EXT:core/Resources/Public/Icons/T3Icons/actions/actions-page-open.svg"/>
+						<core:icon identifier="actions-page-open"/>
 					</button>
 				</li>
 			</f:if>
 			<li>
 				<button type="button" class="btn search-button">
-					<fe:svg source="EXT:core/Resources/Public/Icons/T3Icons/actions/actions-filter.svg"/>
+					<core:icon identifier="actions-filter"/>
 				</button>
 			</li>
 
 			<f:if condition="{mounts}">
 				<li>
 					<button type="button" class="btn site-root-button">
-						<fe:svg source="EXT:core/Resources/Public/Icons/T3Icons/apps/apps-pagetree-page-domain.svg"/>
+						<core:icon identifier="apps-pagetree-page-domain"/>
 					</button>
 				</li>
 			</f:if>
 			<li>
 				<button type="button" class="btn t3-frontend-editing__page-tree-refresh">
-					<fe:svg source="EXT:core/Resources/Public/Icons/T3Icons/actions/actions-refresh.svg"/>
+					<core:icon identifier="actions-refresh"/>
 				</button>
 			</li>
 		</ul>