feat: Add wrapper parameter to goldenTest function

[w3ggy]

Description

Possible fix of the #86. The cause of the issue is that we need to wrap up the code of the test body which is launched inside another zone in custom zone. There is no strict way in the current method signature to pass the wrapper.

The proposed solution from the thread

              pumpBeforeTest: (tester) async {
                await withClock(
                  clock ?? Clock.fixed(DateTime(2025, 12, 10)),
                  () async => pumpBeforeTest(tester),
                );
              },
              pumpWidget: (tester, widget) async {
                await withClock(
                  clock ?? Clock.fixed(DateTime(2025, 12, 10)),
                  () async => tester.pumpWidget(widget),
                );
              },

is not good enough because we have to wrap up the next pumps as well. It is more just like a proposal but this one is working on my end. I am not sure what kind of tests I can (should) add for this tweak.

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore

[w3ggy]

I added an example but I cannot update goldens inside example using workflow https://github.com/w3ggy/alchemist/actions/runs/20094102542
As I understand, it runs only test from the root but not in example