global: fix theme situation and clean up cruft while adding more cruft

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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

@@ -51,7 +51,7 @@
                 android:background="@null"
                 android:contentDescription="@string/delete"
                 android:onClick="@{() -> collection.remove(item)}"
-                android:src="@drawable/ic_action_delete_black" />
+                android:src="@drawable/ic_action_delete" />
 
             <TextView
                 android:id="@+id/public_key_label"

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

@@ -44,7 +44,7 @@
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:onClick="@{fragment::onRequestCreateConfig}"
-                app:fab_icon="@drawable/ic_action_edit"
+                app:fab_icon="@drawable/ic_action_edit_inverse"
                 app:fab_size="mini"
                 app:fab_title="@string/create_empty" />
 
@@ -53,7 +53,7 @@
                 android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:onClick="@{fragment::onRequestImportConfig}"
-                app:fab_icon="@drawable/ic_action_open"
+                app:fab_icon="@drawable/ic_action_open_inverse"
                 app:fab_size="mini"
                 app:fab_title="@string/create_from_file" />
         </com.wireguard.android.widget.fab.FloatingActionsMenu>