chore: require node 10 as minimum engine

[faustbrian]

Proposed changes

Follow up to #1245 as we use some features for snapshots that are only available from node 10 and afterwards.

Types of changes

• Build (changes that affect the build system)

Checklist

• I have read the CONTRIBUTING documentation
• Lint and unit tests pass locally with my changes

[codecov-io]

Codecov Report

Merging #1246 into develop will increase coverage by 0.14%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1246      +/-   ##
===========================================
+ Coverage    78.63%   78.78%   +0.14%     
===========================================
  Files          415      415              
  Lines         6966     6966              
  Branches       929      929              
===========================================
+ Hits          5478     5488      +10     
+ Misses        1316     1309       -7     
+ Partials       172      169       -3

Impacted Files	Coverage Δ
...p2p/lib/server/versions/internal/handlers/utils.js	86.66% <0%> (+6.66%)	⬆️
packages/core-forger/lib/manager.js	81.52% <0%> (+9.78%)	⬆️

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