Serialize Dialog tests and fix reducibleMiddlewareToCancel condition polling

[killlilwinters]

Description

This merge request restructures dialog-related tests to run under a shared serialized test registry, addressing isolation issues caused by the global dialog registry state. The change is necessary because multiple dialog and toast tests rely on shared registration APIs (Dialog.register, DialogRegistry.registerToast, _DialogRegistry.get) and can interfere with each other if executed outside a coordinated serialized scope.

Instead of keeping several independent serialized suites, the tests are now grouped under a single DialogRegistryTests container. This makes registry-dependent behavior explicit and reduces flakiness from cross-test contamination. An alternative would have been to remove global/shared registry usage from the tests entirely, but this MR chooses the lighter-weight approach of reorganizing the suite boundaries.

It also tightens one middleware cancellation test by replacing polling-based assertions with direct state checks plus an explicit store synchronization step, making the test less timing-dependent.

Changes Made

• Introduced a new top-level serialized test container:

  @Suite(.serialized)
  struct DialogRegistryTests {}

• Moved existing dialog registry-related suites under that shared container:

  • DialogTests is now nested under DialogRegistryTests
  • ToastDismissCallbackTests is now nested under DialogRegistryTests
  • DialogDSLTests extension target was updated accordingly:

    extension DialogRegistryTests.DialogTests

• Preserved dialog test setup that clears the registry on suite init, but now within the nested suite structure:

  init() {
      Dialog.clearAll()
  }

• Consolidated all registry-dependent dialog/toast coverage under the same serialized execution scope, including:

  • legacy and DSL-based dialog registration
  • toast registration and presentation
  • custom toast icon/custom view behavior
  • toast auto-dismiss callback registration and execution behavior
  • registry lookup behavior for registered/unregistered IDs

• Improved MiddlewareCancellationTests to avoid asynchronous polling when validating cancellation:

  • replaced waitForCondition for the initial loading assertion with direct state verification
  • added await store.wait() after dispatching cancel action
  • verified final state directly after synchronization

  await store.dispatch(Actions.CancelLoading())
  await store.wait()
  success = await store.state.middlewareFlow == .none