feat: awaitable emit

[k-wasniowski]

Add emitAsync method to TypedEvent

Summary

This PR adds a new emitAsync method to the TypedEvent class that allows emitting events and waiting for all handlers (including async handlers) to complete before resolving.

Motivation

The existing emit method is fire-and-forget, which doesn't provide a way to:

• Wait for async event handlers to complete
• Ensure all handlers have finished executing before proceeding
• Handle async workflows that depend on event handler completion

This is particularly useful in scenarios where:

• Event handlers perform async operations (API calls, database queries, etc.)
• The caller needs to know when all event processing is complete
• Sequential processing is required after event emission

This change implements...

• A new feature
• A bug fix
• Other (please specify):

Is this a breaking change?

• Yes
• No

I certify that...

• All relevant unit and integration tests have passed and/or have been updated according to this change.

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• No GAI - Code was written entirely manually without GAI assistance

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