fixes mozilla-mobile#4434 - made close button for collections more ac…

…cessible.

set recommended minimum size for accessibility 48x48, while keeping image size the same
removed margin from button as it was not needed anymore
aligned close button in center of tab to be visual consistent with alignment of favicon and more visual accessible
implemented same visual solution as for mozilla-mobile#4193 - close button for tabs

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

@@ -21,6 +21,7 @@
 
         <ImageView
                 android:id="@+id/collection_tab_icon"
+                android:importantForAccessibility="no"
                 android:layout_width="24dp"
                 android:layout_height="24dp"
                 android:layout_marginTop="23dp"
@@ -62,16 +63,15 @@
 
         <ImageButton
                 android:id="@+id/collection_tab_close_button"
-                android:layout_width="8dp"
-                android:layout_height="8dp"
+                android:layout_width="48dp"
+                android:layout_height="48dp"
                 android:background="?android:attr/selectableItemBackgroundBorderless"
                 android:contentDescription="@string/close_tab"
                 android:src="@drawable/ic_close"
-                android:layout_marginTop="13dp"
-                android:layout_marginEnd="13dp"
                 android:alpha="0.8"
                 app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintTop_toTopOf="parent"/>
+                app:layout_constraintTop_toTopOf="parent"
+                app:layout_constraintBottom_toBottomOf="parent"/>
 
         <View
                 android:id="@+id/divider_line"