Async exception tracking

[Menduist]

Once status-im/nim-chronos#251 is merged, and some time has passed, we should start to integrate it in libp2p API

This will require to think long and hard about how we handle exceptions, and will probably catch a lot of exception bugs

While exception tracking can mostly be added in a backward-compatible manner, that is not the case for async callbacks (for instance, gossipsub validators). We can either breack backward compatibility (requires a 2.0), or just keep the callbacks unchecked (seems reasonable)

Also keep in mind that once exception tracking is in, adding new exceptions will break compatbilitly

[arnetheduck]

Also keep in mind that once exception tracking is in, adding new exceptions will break compatbilitly

Already breaks compatibility if raising a new type (except changes meaning in calling code), albeit at runtime instead of compile-time.

[arnetheduck]

async raises have been merged in chronos, so this is now unblocked

[etan-status]

Have started annotating {.async: (raises).}.

For callbacks, there's a way to allow handler = and new to still accept old-style callbacks while also accept ones that are tagged with (raises) by wrapping the new ones with the old one. That doesn't need a 2.0.