add testnet

[mhxw]

Hello, developer of chainsafe team. Refer to ethermint's testnet branch and the early implementation of my own code to achieve the following points:

1. Generate an Ethereum type account in the genesis.json file.
2. Export the private key in Ethereum format correctly.
3. After testing, you can successfully run multiple nodes.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #382 into development will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           development     #382   +/-   ##
============================================
  Coverage        55.71%   55.71%           
============================================
  Files               35       35           
  Lines             2353     2353           
============================================
  Hits              1311     1311           
  Misses             930      930           
  Partials           112      112           

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[fedekunze]

superseded by #378