Improve builder API

[Menduist]

Building a switch is no easy task. libp2p being a modular system, we have to build 10s of objects, in a particular order, and ideally in a quite generic way

The current builder system has a few flaws:

• It is not modular at all, which means:
  • Code outside of libp2p cannot be integrated into it
  • It needs to import every module of libp2p that it can build, even if the user doesn't care about said module (especially bad when the module imports optional dependencies, like the transports)
  • Every time we add something to libp2p, we also need to add it to this file
• It's quite hard to maintain

With that in mind, we need to find a new system.
A good starting point might be to look at other libp2ps, and how to they build their switches.

Last time I did this exercice, I've seen that they mostly used hard-coded builders like ours, but go-libp2p wanted to switch to a dependency injection pattern.

AFAIK, we don't have a good DI library in Nim, so I've started a PoC a few years ago: #701
However, it's quite rough, and needs more work