Dynamic non-frozen router

### Is your feature request related to a problem?

Hi,

I'm using aiohttp-swagger3 for building of an api interface for the app. Unfortunately I'm not able to change router after application is started. I.e. del_route() not available, add_route() after not working tried also app.router._frozen = False/True. What problems can dynamic configuration cause? I've used such configurations in Tornado long ago and it works fine.

### Describe the solution you'd like

Dynamic router

### Describe alternatives you've considered

Dynamic router

### Related component

Server

### Additional context

_No response_

### Code of Conduct

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