cmd: Add goal node subcommand to generate peer private key

[algorandskiy]

Summary

As part of upcoming p2p deployment we need to register p2p bootstrap nodes in DNS TXT.
This tool allows to generate a new peer private key and print out peer ID (or print it from existing key file with default name).

Test Plan

Tested manually

goal node -d . -d test generate-p2pid
[Data Directory: /Users/algorandskiy/go-algorand]
PeerID: 12D3KooWSPTKMhFqaWMsjNtBG1vWgRd8GXUbUtQt3iX2GQp9bgC5
Private key saved to /Users/algorandskiy/go-algorand/peerIDPrivKey.pem
[Data Directory: test]
PeerID: 12D3KooWJzt2v6g2BtaD5pTLLa2JkA4bnKCAW6b2AmRbqLDPccBg
Private key saved to test/peerIDPrivKey.pem

goal node -d . -d test generate-p2pid
[Data Directory: /Users/algorandskiy/go-algorand]
PeerID: 12D3KooWSPTKMhFqaWMsjNtBG1vWgRd8GXUbUtQt3iX2GQp9bgC5
Used existing key /Users/algorandskiy/go-algorand/peerIDPrivKey.pem
[Data Directory: test]
PeerID: 12D3KooWJzt2v6g2BtaD5pTLLa2JkA4bnKCAW6b2AmRbqLDPccBg
Used existing key test/peerIDPrivKey.pem

[codecov]

Codecov Report

Attention: Patch coverage is 4.00000% with 24 lines in your changes missing coverage. Please review.

Project coverage is 56.26%. Comparing base (edda2ee) to head (375efad).
Report is 3 commits behind head on master.

Files	Patch %	Lines
cmd/goal/p2pid.go	0.00%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6078      +/-   ##
==========================================
+ Coverage   55.95%   56.26%   +0.30%     
==========================================
  Files         488      489       +1     
  Lines       69602    69627      +25     
==========================================
+ Hits        38945    39173     +228     
+ Misses      27967    27802     -165     
+ Partials     2690     2652      -38     

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[jasonpaulos]

Makes sense, just one comment

[cce]

LGTM, though it may make sense to move this to be a goal subcommand later, for node operators who want to generate persistent p2p IDs.

[algorandskiy]

Like goal node -d /a/b/c generatep2pkey ?

[algorandskiy]

Implemented as goal node generate-p2pid subcommand.