Revert Promise.resolve in event handlers

[jmorrell-cloudflare]

Following up from #186

Adding these back emits these logs in tests:

workerd/io/worker.c++:1020: info: console warning; message = An event handler returned a promise that will be ignored. Event handlers should not have a return value and should not be async functions.

I'm not sure how to best resolve

[changeset-bot]

🦋 Changeset detected

Latest commit: 4a838e0

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
agents	Patch
hono-agents	Patch

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[threepointone]

I'll take this over and fix it, thanks for kicking it off!

[threepointone]

pushed changes, wanna test and make sure I didn't break anything?

[threepointone]

hide whitespace when looking at the diff, and my changes will be more obvious

[threepointone]

hide whitespace when looking at the diff, and my changes will be more obvious