refactor: use Coins.Config by reference

[faustbrian]

Resolves #458

Only peers will not be used by reference because some coins use WebSockets or require peers in several places which would lead to having to implement some kind of watchers to recreate all of those instances. In those cases, it is advised to simply recreate the whole coin instance to ensure that all previous instances are destroyed and won't interfere with the new one.

[codecov]

Codecov Report

Merging #461 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #461   +/-   ##
=======================================
  Coverage   72.40%   72.40%           
=======================================
  Files          52       52           
  Lines         993      993           
  Branches       70       70           
=======================================
  Hits          719      719           
  Misses        247      247           
  Partials       27       27           

Flag	Coverage Δ
#unit	72.40% <ø> (ø)

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