impl ToSocketAddrs for Hostname (and possibly other NetAddress variants)

[tnull]

In #2134 we added the FromStr trait implementation to NetAddress.

As a follow-up it would be nice to also add a ToSocketAddrs implementation to allow easy resolution for our NetAdresses, which would be useful for the Hostname variant in particular.

This would also allow us to get rid of the NetAddress newtype in LDK Node, which currently makes use of ToSocketAddrs (cf. https://github.com/lightningdevkit/ldk-node/blob/a9bb2e9c5b9892213b244bc2fb474a5fe0c76802/src/types.rs#L360-L385).

[slanesuke]

I'll take this one as my first issue if that works?

[tnull]

I'll take this one as my first issue if that works?

Sure, go for it!