feat: Add neutrino mode client support

[masterchief164]

This PR adds client-side support for the neutrino mode

[codecov]

Codecov Report

Patch coverage: 50.70% and no project coverage change.

Comparison is base (b005869) 69.55% compared to head (4c3681b) 69.56%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #1160    +/-   ##
========================================
  Coverage   69.55%   69.56%            
========================================
  Files         158      159     +1     
  Lines       26603    26877   +274     
========================================
+ Hits        18505    18696   +191     
- Misses       8098     8181    +83     

Impacted Files	Coverage Δ
lib/bcoin-browser.js	0.00% <0.00%> (ø)
lib/bcoin.js	0.00% <0.00%> (ø)
lib/blockchain/layout.js	100.00% <ø> (ø)
lib/indexer/filterindexer.js	64.81% <0.00%> (-29.78%)	⬇️
lib/blockchain/chaindb.js	77.92% <39.13%> (-0.53%)	⬇️
lib/net/pool.js	60.05% <42.64%> (+0.80%)	⬆️
lib/net/peer.js	71.96% <50.00%> (+0.76%)	⬆️
lib/node/neutrino.js	76.92% <76.92%> (ø)
lib/blockchain/chain.js	73.50% <87.50%> (+0.16%)	⬆️

... and 3 files with indirect coverage changes

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