feat(side-dag): implement side_dag CLI command

[glevco]

Depends on #1040

Motivation

Implement a new side_dag CLI command that is able to run two independent full nodes, each in its own separate process. The command accepts the same options as the run_node command, however options can be duplicate with a --side-dag prefix. Each full node is configured with the respective set of options. Processes are automatically terminated when one of the full nodes exits.

Here's an example on how this command could be used:

 $ python -m hathor side_dag
     --testnet
     --procname-prefix testnet-
     --memory-storage
     --disable-logs
     --side-dag-config-yaml ./my-side-dag.yml
     --side-dag-procname-prefix my-side-dag-
     --side-dag-memory-storage
     --side-dag-json-logs

Acceptance Criteria

• Implement new cli.util.process_logging_options().
• Change execute_from_command_line() so it supports modules opting out of the setup_logging() call.
• Update create_parser() so it accepts a custom env var prefix.
• Add support to disabling logs.
• Implement side_dag CLI command.
• Implement HathorSettings.GENESIS_TOKENS calculated property, removing the GENESIS_TOKENS constant.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.95%. Comparing base (b20be70) to head (2310be5).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1039      +/-   ##
==========================================
+ Coverage   84.87%   84.95%   +0.08%     
==========================================
  Files         300      300              
  Lines       22943    22943              
  Branches     3470     3470              
==========================================
+ Hits        19473    19492      +19     
+ Misses       2778     2766      -12     
+ Partials      692      685       -7     

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