Update M3 IconButton unselected focused opacity (#117321)

* Bottom App Bar M3 background color fix

* update test

* test update

* remove whitespace

* Update IconButton unselected focused opacity

* Delete generated_plugins.cmake

Author: Eilidh Southren

dev/tools/gen_defaults/data/icon_button.json

@@ -18,7 +18,7 @@
   "md.comp.icon-button.state-layer.size": 40.0,
   "md.comp.icon-button.unselected.focus.icon.color": "onSurfaceVariant",
   "md.comp.icon-button.unselected.focus.state-layer.color": "onSurfaceVariant",
-  "md.comp.icon-button.unselected.focus.state-layer.opacity": "md.sys.state.hover.state-layer-opacity",
+  "md.comp.icon-button.unselected.focus.state-layer.opacity": "md.sys.state.focus.state-layer-opacity",
   "md.comp.icon-button.unselected.hover.icon.color": "onSurfaceVariant",
   "md.comp.icon-button.unselected.hover.state-layer.color": "onSurfaceVariant",
   "md.comp.icon-button.unselected.hover.state-layer.opacity": "md.sys.state.hover.state-layer-opacity",

packages/flutter/lib/src/material/icon_button.dart

@@ -1011,7 +1011,7 @@ class _IconButtonDefaultsM3 extends ButtonStyle {
         return _colors.onSurfaceVariant.withOpacity(0.08);
       }
       if (states.contains(MaterialState.focused)) {
-        return _colors.onSurfaceVariant.withOpacity(0.08);
+        return _colors.onSurfaceVariant.withOpacity(0.12);
       }
       if (states.contains(MaterialState.pressed)) {
         return _colors.onSurfaceVariant.withOpacity(0.12);