Visual design: small icon version in omnibar (#6015)

Task/Issue URL:
https://app.asana.com/1/137249556945/project/1174433894299346/task/1210056293401143

### Description
Update back arrow as small icon

### UI changes
| New  | Old |
| ------ | ----- |

|![Screenshot_20250506_171621](https://github.com/user-attachments/assets/eb440caa-c9b5-4a27-9c06-aa7e0bc0529e)|![Screenshot_20250506_172238](https://github.com/user-attachments/assets/76f0f056-56e1-4831-bd33-8ea17008c788)|

|![Screenshot_20250506_171643](https://github.com/user-attachments/assets/7efd1d02-6c9b-4913-99d4-60448f743a18)|![Screenshot_20250506_172228](https://github.com/user-attachments/assets/0074e1e0-77e8-43ef-a8aa-2729a1050298)|

Author: malmstein

app/src/main/res/layout/view_fade_omnibar.xml

@@ -152,6 +152,7 @@
                                 android:layout_height="@dimen/toolbarIcon"
                                 android:layout_gravity="center"
                                 android:gravity="center"
+                                android:scaleType="center"
                                 android:importantForAccessibility="no"
                                 android:padding="@dimen/keyline_2"
                                 android:src="@drawable/ic_find_search_small_24" />
@@ -165,7 +166,8 @@
                                 android:background="@drawable/selectable_item_experimental_background"
                                 android:contentDescription="@string/back"
                                 android:gravity="center"
-                                android:src="@drawable/ic_arrow_left_24"
+                                android:scaleType="center"
+                                android:src="@drawable/ic_arrow_left_small_24"
                                 android:visibility="gone" />
 
                             <ImageView

common/common-ui/src/main/res/drawable/ic_arrow_left_small_24.xml

@@ -0,0 +1,25 @@
+<!--
+  ~ Copyright (c) 2025 DuckDuckGo
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~     http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    android:width="24dp"
+    android:height="24dp"
+    android:viewportWidth="24"
+    android:viewportHeight="24">
+  <path
+      android:pathData="M10.977,4.881a0.75,0.75 0,1 0,-1.06 -1.06L3.765,9.97a2.55,2.55 0,0 0,0 3.607l6.152,6.152a0.75,0.75 0,0 0,1.061 -1.06l-6.145,-6.146L20.25,12.5a0.75,0.75 0,1 0,-0.002 -1.5l-15.415,0.024 6.143,-6.143Z"
+      android:fillColor="?attr/daxColorPrimaryIcon"/>
+</vector>