Enhancement: add after_startup and before_shutdown hooks

[betaboon]

Summary

I need to run a task after the app has been fully setup.
thus on_startup is to early.

Talking to @cofin on discord revealed the following:

• Litestar.lifespan seems to be the right location to add this
• after_startup and before_shutdown should be added to the app/appconfig objects

Basic Example

No response

Drawbacks and Impact

No response

Unresolved questions

No response

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