Fix filled color is wrong for a focused and hovered TextField (#146976)

## Description

This PR fixes the filled color for a focused and hovered text field.
Before this PR, the filled color for a focused text field did not change when hovered, after this PR the filled color is blended with the hover color.

The change removes a `isFocused` check which deactivated the blending. This check was introduced in flutter/flutter#32776, at that time it was needed because there was also a focus color animation. Sometimes later, the focus animation was removed, see flutter/flutter#33062, but the flag was not removed.

**Before**:

https://github.com/flutter/flutter/assets/840911/9698ba82-eb67-428a-8635-8054a4b8dfaf

**After**:

https://github.com/flutter/flutter/assets/840911/4c03a137-360d-4612-8946-765d7b5c698d

## Related Issue

Fixes flutter/flutter#146573

## Tests

Adds 1 tests.

Author: bleroux

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

@@ -1950,7 +1950,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
   }
 
   Color _getHoverColor(ThemeData themeData) {
-    if (decoration.filled == null || !decoration.filled! || isFocused || !decoration.enabled) {
+    if (decoration.filled == null || !decoration.filled! || !decoration.enabled) {
       return Colors.transparent;
     }
     return decoration.hoverColor ?? themeData.inputDecorationTheme.hoverColor ?? themeData.hoverColor;

packages/flutter/test/material/input_decorator_test.dart

@@ -350,7 +350,7 @@ void main() {
             ..path(
               style: PaintingStyle.fill,
               color: theme.colorScheme.surfaceContainerHighest,
-            )
+            ),
           );
         });
 
@@ -409,7 +409,7 @@ void main() {
             ..path(
               style: PaintingStyle.fill,
               color: theme.colorScheme.onSurface.withOpacity(0.04),
-            )
+            ),
           );
         });
 
@@ -470,7 +470,7 @@ void main() {
             ..path(
               style: PaintingStyle.fill,
               color: Color.alphaBlend(theme.hoverColor, theme.colorScheme.surfaceContainerHighest),
-            )
+            ),
           );
         });
 
@@ -530,7 +530,32 @@ void main() {
             ..path(
               style: PaintingStyle.fill,
               color: theme.colorScheme.surfaceContainerHighest,
-            )
+            ),
+          );
+        });
+
+        testWidgets('container has correct color when focused and hovered', (WidgetTester tester) async {
+          // Regression test for https://github.com/flutter/flutter/issues/146573.
+          await tester.pumpWidget(
+            buildInputDecorator(
+              isFocused: true,
+              isHovering: true,
+              decoration: const InputDecoration(
+                filled: true,
+                labelText: labelText,
+                helperText: helperText,
+              ),
+            ),
+          );
+
+          final ThemeData theme = Theme.of(tester.element(findDecorator()));
+          final Color focusColor = theme.colorScheme.surfaceContainerHighest;
+          final Color hoverColor = theme.hoverColor;
+          expect(findBorderPainter(), paints
+            ..path(
+              style: PaintingStyle.fill,
+              color: Color.alphaBlend(hoverColor, focusColor),
+            ),
           );
         });
 
@@ -607,7 +632,7 @@ void main() {
             ..path(
               style: PaintingStyle.fill,
               color: theme.colorScheme.surfaceContainerHighest,
-            )
+            ),
           );
         });
 
@@ -729,7 +754,7 @@ void main() {
           expect(findBorderPainter(), paints
             ..path(
               style: PaintingStyle.stroke,
-            )
+            ),
           );
         });
 
@@ -784,7 +809,7 @@ void main() {
           expect(findBorderPainter(), paints
             ..path(
               style: PaintingStyle.stroke,
-            )
+            ),
           );
         });
 
@@ -840,7 +865,7 @@ void main() {
           expect(findBorderPainter(), paints
             ..path(
               style: PaintingStyle.stroke,
-            )
+            ),
           );
         });
 
@@ -896,7 +921,7 @@ void main() {
           expect(findBorderPainter(), paints
             ..path(
               style: PaintingStyle.stroke,
-            )
+            ),
           );
         });
 
@@ -969,7 +994,7 @@ void main() {
           expect(findBorderPainter(), paints
             ..path(
               style: PaintingStyle.stroke,
-            )
+            ),
           );
         });