WI01076374 - Currency Manager .NET10 Fix

[FahmiFuzi]

This pull request introduces extensibility improvements to the data binding infrastructure in Windows Forms, specifically targeting how BindingContext manages its internal collection of BindingManagerBase instances. The main goal is to allow subclasses to customize behavior when a new binding manager is added, and to expose a helper for re-wiring parent-child event handlers in related currency managers. This refactoring makes it easier for downstream consumers (such as custom binding contexts) to implement advanced scenarios without modifying the base collection logic.

Extensibility for binding manager addition:

• Added a new protected virtual method OnListManagerAdded(BindingManagerBase bindingManagerBase) to BindingContext, which is invoked whenever a new BindingManagerBase is added or refreshed. The default implementation is a no-op, allowing subclasses to override and inject custom logic at this point.
• Updated EnsureListManager in BindingContext to call OnListManagerAdded after adding a new manager.

Helpers for advanced event wiring:

• Introduced a protected static helper method RewireRelatedCurrencyManagerParent(BindingManagerBase bindingManagerBase) in BindingContext. This method allows subclasses to rewire parent event subscriptions for related currency managers, supporting scenarios previously handled by custom hashtable logic in .NET Framework. [1] [2]
• Added the internal method RewireParentChangeHandler() to RelatedCurrencyManager, which detaches and re-attaches the correct parent event handlers and primes the child manager with the parent's current state. This supports the new extensibility point in BindingContext.

Public API surface:

• Registered the new methods BindingContext.OnListManagerAdded and BindingContext.RewireRelatedCurrencyManagerParent in the public API file.