[TASK] Replace FontAwesome icons with typo3 icons

To provide a consistent look&feel and to eventually phase out
FontAwesome in the TYPO3 backend, all remaining fa-* icons are replaced
with their counterparts from the @typo3/icons package.

The CSS class `icon-emphasized` is introduced as a drop-in replacement
for the `fa-stack` construct:

```
<span class="icon-emphasized">
    <core:icon identifier="my-icon-identifier" size="small"/>
</span>
```

The removal of the FontAwesome integration will follow in a separate
patch.

Resolves: #97877
Releases: main
Change-Id: I0e9ca1e4a918b3f44969ea9886ec0cd1e56d78be
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75041
Tested-by: core-ci <[email protected]>
Tested-by: Nikita Hovratov <[email protected]>
Tested-by: Benni Mack <[email protected]>
Reviewed-by: Nikita Hovratov <[email protected]>
Reviewed-by: Benni Mack <[email protected]>

Resources/Private/Partials/ObjectBrowserTree.html

@@ -19,7 +19,7 @@
                             data-action-submit="$form"
                             data-form-values="{ts:astCurrentObjectPathAsJson(currentObjectPath: currentObjectPath, key: '{type}Collapse')}"
                         >
-                            <i class="fa"></i>
+                            <core:icon identifier="actions-caret-down"/>
                         </a>
                     </f:then>
                     <f:else>
@@ -29,7 +29,7 @@
                             data-action-submit="$form"
                             data-form-values="{ts:astCurrentObjectPathAsJson(currentObjectPath: currentObjectPath, key: '{type}Expand')}"
                         >
-                            <i class="fa"></i>
+                            <core:icon identifier="actions-caret-right"/>
                         </a>
                     </f:else>
                 </f:if>