Improve and optimize non-uniform Borders. (#124417)

~~Using the same priority order as a Border without borderRadius, it is possible to draw them on top of each other. This is better than the current behavior (crash!) and would work well for a "one color on top, another on bottom" scenario.~~

~~With this, if approved, we move the current number of possible exceptions from 4 to 1 (`BoxShape.circle` + `borderRadius`).~~

~~It is kind of odd how `borderRadius.zero` to `borderRadius != BorderRadius.zero` change, but I think it is better than crashing. Alternatively, we just remove the "original function" and see if any goldens are affected.~~

<img width="448" alt="image" src="https://user-images.githubusercontent.com/351125/236550350-7499d758-5b44-40e6-9105-32671eb21998.png">

Another one for @gspencergoog. If this works, we could make the paint method public and re-use in the InputBorder PR (if that's also approved). Single line fix.

packages/flutter/test/material/data_table_test.dart

@@ -1750,7 +1750,7 @@ void main() {
     );
     expect(
       find.ancestor(of: find.byType(Table), matching: find.byType(Container)),
-      paints..drrect(color: borderColor),
+      paints..path(color: borderColor),
     );
     expect(
       tester.getTopLeft(find.byType(Table)),

packages/flutter/test/material/divider_test.dart

@@ -136,8 +136,9 @@ void main() {
 
   testWidgets('Vertical Divider Test 2', (WidgetTester tester) async {
     await tester.pumpWidget(
-      const MaterialApp(
-        home: Material(
+      MaterialApp(
+        theme: ThemeData(useMaterial3: false),
+        home: const Material(
           child: SizedBox(
             height: 24.0,
             child: Row(

packages/flutter/test/painting/border_test.dart

@@ -273,7 +273,7 @@ void main() {
     expect(error.diagnostics.length, 1);
     expect(
       error.diagnostics[0].toStringDeep(),
-      'A Border can only draw strokeAlign different than\nBorderSide.strokeAlignInside on borders with uniform colors and\nstyles.\n',
+      'A Border can only draw strokeAlign different than\nBorderSide.strokeAlignInside on borders with uniform colors.\n',
     );
   });
 
@@ -341,8 +341,8 @@ void main() {
 
     // This falls into non-uniform border because of strokeAlign.
     await tester.pumpWidget(buildWidget(border: allowedBorderVariations));
-    expect(tester.takeException(), isNull,
-        reason: 'Border with non-uniform strokeAlign should not fail.');
+    expect(tester.takeException(), isAssertionError,
+        reason: 'Border with non-uniform strokeAlign should fail.');
 
     await tester.pumpWidget(buildWidget(
       border: allowedBorderVariations,
@@ -364,8 +364,8 @@ void main() {
         borderRadius: BorderRadius.circular(25),
       ),
     );
-    expect(tester.takeException(), isAssertionError,
-        reason: 'Border with non-uniform styles should fail with borderRadius.');
+    expect(tester.takeException(), isNull,
+        reason: 'Border with non-uniform styles should work with borderRadius.');
 
     await tester.pumpWidget(
       buildWidget(
@@ -381,6 +381,24 @@ void main() {
     expect(tester.takeException(), isAssertionError,
         reason: 'Border with non-uniform colors should fail with borderRadius.');
 
+    await tester.pumpWidget(
+      buildWidget(
+        border: const Border(bottom: BorderSide(width: 0)),
+        borderRadius: BorderRadius.zero,
+      ),
+    );
+    expect(tester.takeException(), isNull,
+        reason: 'Border with a side.width == 0 should work without borderRadius (hairline border).');
+
+    await tester.pumpWidget(
+      buildWidget(
+        border: const Border(bottom: BorderSide(width: 0)),
+        borderRadius: BorderRadius.circular(40),
+      ),
+    );
+    expect(tester.takeException(), isAssertionError,
+        reason: 'Border with width == 0 and borderRadius should fail (hairline border).');
+
     // Tests for BorderDirectional.
     const BorderDirectional allowedBorderDirectionalVariations = BorderDirectional(
       start: BorderSide(width: 5),
@@ -390,7 +408,7 @@ void main() {
     );
 
     await tester.pumpWidget(buildWidget(border: allowedBorderDirectionalVariations));
-    expect(tester.takeException(), isNull);
+    expect(tester.takeException(), isAssertionError);
 
     await tester.pumpWidget(buildWidget(
       border: allowedBorderDirectionalVariations,