Add libp2p connection Firewall

[Nashatyrev]

PR Description

Add a Libp2p Firewall class as a first line handler for every Connection. Incorporate @ajsutton tweaks he made in this PR: libp2p/jvm-libp2p#127

Documentation

• I thought about documentation and added the documentation label to this PR if updates are required.

[ajsutton]

I definitely like this approach so we can control the settings we need in Teku. Have tested it out and syncing blocks works with a local network. I tried with a throttled connection and did start getting disconnections but it seems pretty reasonable given I throttled the server since it was conveniently in a docker container and it had 35 other peers on just a 256kbit connection.

When the peer was disconnected through we got an error logged in the server which we should probably find a way to handle cleanly:

teku_1           | 2020-07-30 05:21:02.123 | nioEventLoopGroup-3-3     | ERROR | NoiseXXSecureChannel           | Unexpected error in Noise channel
teku_1           | io.netty.handler.timeout.WriteTimeoutException: null

I'm also going to look into adjusting Teku so that it actually uses the returned future when writing requested blocks - currently it just sends them as fast as it can but should actually pay attention to when the response stream becomes unwritable and delay loading the next block to send.

[ajsutton]

I'm not seeing any disconnections with a reasonably 1024Kbit upload limit on the serving node so I'd say these are workable starting values and we don't need to wait for the change I mentioned about waiting for blocks to finish writing.

I think we should fix the error message before merging this though.

[ajsutton]

Reran the test and confirmed we don't log errors when disconnecting which is great.

LGTM.