upgrade to libp2p 0.52 (#4431)

## Issue Addressed

Upgrade libp2p to v0.52

## Proposed Changes
- **Workflows**: remove installation of `protoc`
- **Book**: remove installation of `protoc`
- **`Dockerfile`s and `cross`**: remove custom base `Dockerfile` for cross since it's no longer needed. Remove `protoc` from remaining `Dockerfiles`s
- **Upgrade `discv5` to `v0.3.1`:** we have some cool stuff in there: no longer needs `protoc` and faster ip updates on cold start
- **Upgrade `prometheus` to `0.21.0`**, now it no longer needs encoding checks
- **things that look like refactors:** bunch of api types were renamed and need to be accessed in a different (clearer) way
- **Lighthouse network**
	- connection limits is now a behaviour
	- banned peers no longer exist on the swarm level, but at the behaviour level
	- `connection_event_buffer_size` now is handled per connection with a buffer size of 4
	- `mplex` is deprecated and was removed
	- rpc handler now logs the peer to which it belongs

## Additional Info

Tried to keep as much behaviour unchanged as possible. However, there is a great deal of improvements we can do _after_ this upgrade:
- Smart connection limits: Connection limits have been checked only based on numbers, we can now use information about the incoming peer to decide if we want it
- More powerful peer management: Dial attempts from other behaviours can be rejected early
- Incoming connections can be rejected early
- Banning can be returned exclusively to the peer management: We should not get connections to banned peers anymore making use of this
- TCP Nat updates: We might be able to take advantage of confirmed external addresses to check out tcp ports/ips


Co-authored-by: Age Manning <Age@AgeManning.com>
Co-authored-by: Akihito Nakano <sora.akatsuki@gmail.com>

beacon_node/lighthouse_network/src/rpc/self_limiter.rs

@@ -64,7 +64,7 @@ impl<Id: ReqId, TSpec: EthSpec> SelfRateLimiter<Id, TSpec> {
     }
 
     /// Checks if the rate limiter allows the request. If it's allowed, returns the
-    /// [`NetworkBehaviourAction`] that should be emitted. When not allowed, the request is delayed
+    /// [`ToSwarm`] that should be emitted. When not allowed, the request is delayed
     /// until it can be sent.
     pub fn allows(
         &mut self,
@@ -95,7 +95,7 @@ impl<Id: ReqId, TSpec: EthSpec> SelfRateLimiter<Id, TSpec> {
     }
 
     /// Auxiliary function to deal with self rate limiting outcomes. If the rate limiter allows the
-    /// request, the [`NetworkBehaviourAction`] that should be emitted is returned. If the request
+    /// request, the [`ToSwarm`] that should be emitted is returned. If the request
     /// should be delayed, it's returned with the duration to wait.
     fn try_send_request(
         limiter: &mut RateLimiter,