Optimize the display of the Overlay on the Slider (#139021)

## Description

Automatic focus request on Slider value change prevents Overlay from correctly handling hover events.

Fixes #139281

### Before

![slider3](https://github.com/flutter/flutter/assets/38378650/815e12a4-ccaf-4b99-8480-6cbdc97a91bd)

### After

![slider4](https://github.com/flutter/flutter/assets/38378650/473eca22-0308-4964-8368-b0c158ae30eb)

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

@@ -666,7 +666,6 @@ class _SliderState extends State<Slider> with TickerProviderStateMixin {
     final double lerpValue = _lerp(value);
     if (lerpValue != widget.value) {
       widget.onChanged!(lerpValue);
-      _focusNode?.requestFocus();
     }
   }
 
@@ -1376,8 +1375,8 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     if (hovered && hoveringThumb) {
       _state.overlayController.forward();
     } else {
-      // Only remove overlay when Slider is unfocused.
-      if (!hasFocus) {
+      // Only remove overlay when Slider is inactive and unfocused.
+      if (!_active && !hasFocus) {
         _state.overlayController.reverse();
       }
     }

packages/flutter/test/material/slider_test.dart

@@ -3396,6 +3396,99 @@ void main() {
     expect(dragStarted, false);
   });
 
+  // Regression test for https://github.com/flutter/flutter/issues/139281
+  testWidgetsWithLeakTracking('Slider does not request focus when the value is changed', (WidgetTester tester) async {
+    double value = 0.5;
+    await tester.pumpWidget(MaterialApp(
+      home: Material(
+        child: Center(
+          child: StatefulBuilder(builder: (BuildContext context, StateSetter setState) {
+            return Slider(
+                value: value,
+                onChanged: (double newValue) {
+                  setState(() {
+                    value = newValue;
+                  });
+                }
+            );
+          }),
+        ),
+      ),
+    ));
+    // Initially, the slider does not have focus whe enabled and not tapped.
+    await tester.pumpAndSettle();
+    expect(value, equals(0.5));
+    // Get FocusNode from the state of the slider to include auto-generated FocusNode.
+    // ignore: avoid_dynamic_calls, invalid_assignment
+    final FocusNode focusNode = (tester.firstState(find.byType(Slider)) as dynamic).focusNode;
+    // The slider does not have focus.
+    expect(focusNode.hasFocus, false);
+    final Offset sliderCenter = tester.getCenter(find.byType(Slider));
+    final Offset tapLocation = Offset(sliderCenter.dx + 50, sliderCenter.dy);
+    // Tap on the slider to change the value.
+    final TestGesture gesture = await tester.createGesture();
+    await gesture.addPointer();
+    await gesture.down(tapLocation);
+    await gesture.up();
+    await tester.pumpAndSettle();
+    expect(value, isNot(equals(0.5)));
+    // The slider does not have have focus after the value is changed.
+    expect(focusNode.hasFocus, false);
+  });
+
+  // Regression test for https://github.com/flutter/flutter/issues/139281
+  testWidgetsWithLeakTracking('Overlay remains when Slider thumb is interacted', (WidgetTester tester) async {
+    double value = 0.5;
+    const Color overlayColor = Color(0xffff0000);
+    await tester.pumpWidget(MaterialApp(
+      home: Material(
+        child: Center(
+          child: StatefulBuilder(builder: (BuildContext context, StateSetter setState) {
+            return Slider(
+                value: value,
+                overlayColor: const MaterialStatePropertyAll<Color?>(overlayColor),
+                onChanged: (double newValue) {
+                  setState(() {
+                    value = newValue;
+                  });
+                }
+            );
+          }),
+        ),
+      ),
+    ));
+    // Slider does not have overlay when enabled and not tapped.
+    await tester.pumpAndSettle();
+    expect(
+      Material.of(tester.element(find.byType(Slider))),
+      isNot(paints..circle(color: overlayColor)),
+    );
+    final Offset sliderCenter = tester.getCenter(find.byType(Slider));
+    // Tap and hold down on the thumb to keep it active.
+    final TestGesture gesture = await tester.createGesture();
+    await gesture.addPointer();
+    await gesture.down(sliderCenter);
+    await tester.pumpAndSettle();
+    expect(
+      Material.of(tester.element(find.byType(Slider))),
+      paints..circle(color: overlayColor),
+    );
+    // Hover on the slider but outside the thumb.
+    await gesture.moveTo(tester.getTopLeft(find.byType(Slider)));
+    await tester.pumpAndSettle();
+    expect(
+      Material.of(tester.element(find.byType(Slider))),
+      paints..circle(color: overlayColor),
+    );
+    // Tap up on the slider.
+    await gesture.up();
+    await tester.pumpAndSettle();
+    expect(
+      Material.of(tester.element(find.byType(Slider))),
+      isNot(paints..circle(color: overlayColor)),
+    );
+  });
+
   testWidgetsWithLeakTracking('Overlay appear only when hovered on the thumb on desktop', (WidgetTester tester) async {
     double value = 0.5;
     const Color overlayColor = Color(0xffff0000);