Fire an extension event before unloading extensions

Summary

As a follow up to [this feature]( there should be an event that fires _before unloading_ extensions.

Basic Example

_No response_

Motivation

If we want to properly cleanup extension related resources when auto reload is enabled (developing an extension), we should be able to get an event before unloading them. Additionally, unloading event better be a filter than an action.

Detailed Design

Introduce extensions.unloading event

Requirements List

Must Have:

• Fires before unloading
• Blocking (filter)

Should Have:

• Could Have:

• Non-blocking version

Won't Have:
• Drawbacks

Blocking events can freeze the server if expensive?

Alternatives

Non-blocking only version, but it might still cause some leaks if resources are not properly cleaned up.

Adoption Strategy

Nothing changes.

Unresolved Questions

_No response_