p2p: do not advertise private and non-routable addresses

[algorandskiy]

Summary

When p2p net listens on all interfaces ("0.0.0.0:0", ":0", ":N"), it advertises everything including loopback and private interface addresses. The solution is to handle this specification and apply libp2p's AddressFactory filter.

Note, when some specific address is set like loopback or a private interface, it recognized as intentional action and no filters applied. This allows to all unit tests starting network on "127.0.0.1:0" to continue to operate, as well allows private nets to run if NetAddress is set appropriate (say to "10.1.0.101:0").

During algonet testing I found EC2 instances only have loopback and a private 172.31.x.x addresses so that filtered.
libp2p has address observation facility (part of netidentity) that reports addresses seen at least 4 times (activated() piece) in last 30 minutes (TTL piece).
This means we need at least 4 p2p bootstrap nodes to allow other nodes to advertise their observed addresses over DHT.

Test Plan

1. Added unit tests for addressFilter' function and for MakeHostwith differentNetAddress` specifications.
2. Successfully tested with algonet the following subset of s1-p2p (8 relays, 5 part, 5 non-part nodes):

PARAMS=-w 5 -R 8 -N 5 -n 5 --npn-algod-nodes 5 --node-template node.json --relay-template relay.json --non-participating-node-template nonPartNode.json

with 4 of 8 relays being p2p bootstrap nodes (via DNS TXT) and with all nodes "EnableDHTProviders": true. I was able to add an extra node with "GossipFanout": 8 to this network and have it connected to all 8 relays despite the fact only 8 are registered in DNS.

[codecov]

Codecov Report

Attention: Patch coverage is 61.11111% with 21 lines in your changes missing coverage. Please review.

Project coverage is 56.23%. Comparing base (d2c4ca7) to head (0453241).

Files	Patch %	Lines
network/p2p/p2p.go	61.11%	17 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6092      +/-   ##
==========================================
- Coverage   56.26%   56.23%   -0.03%     
==========================================
  Files         489      489              
  Lines       69637    69691      +54     
==========================================
+ Hits        39182    39192      +10     
- Misses      27796    27831      +35     
- Partials     2659     2668       +9     

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[jasonpaulos]

Looks good just some nits