standalone libp2p-peerbook integration - BC core changes

[andymck]

Changes to accompany standalone peerbook integration PR: helium/erlang-libp2p#265

[codecov]

Codecov Report

Merging #413 into master will decrease coverage by 6.99%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #413      +/-   ##
==========================================
- Coverage   69.11%   62.11%   -7.00%     
==========================================
  Files          72       72              
  Lines        7589     7589              
==========================================
- Hits         5245     4714     -531     
- Misses       2344     2875     +531     

Impacted Files	Coverage Δ
src/blockchain_sup.erl	94.11% <ø> (ø)
src/blockchain_swarm.erl	50.00% <ø> (ø)
src/cli/blockchain_cli_peer.erl	26.80% <0.00%> (ø)
src/poc/blockchain_poc_target_v3.erl	0.00% <0.00%> (-93.75%)	⬇️
src/poc/blockchain_poc_path_v3.erl	0.00% <0.00%> (-89.10%)	⬇️
src/poc/blockchain_poc_target_v2.erl	0.00% <0.00%> (-89.02%)	⬇️
src/poc/blockchain_poc_path_v2.erl	0.00% <0.00%> (-88.89%)	⬇️
src/poc/blockchain_poc_path_v4.erl	0.00% <0.00%> (-88.82%)	⬇️
src/handlers/blockchain_gossip_handler.erl	51.61% <0.00%> (-12.91%)	⬇️
src/blockchain_utils.erl	85.57% <0.00%> (-7.70%)	⬇️
... and 6 more

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[evanmcc]

gonna close this for now, but might be worth bringing it back at some point