[config] Clean up config

[Liuhaai]

Description

• config.Default.Genesis is changed to genesis.Default
• p2p.Network is changed to p2p.Config

Type of change

Please delete options that are not relevant.

• [] Bug fix (non-breaking change which fixes an issue)
• [] New feature (non-breaking change which adds functionality)
• Code refactor or improvement
• [] Breaking change (fix or feature that would cause a new or changed behavior of existing functionality)
• [] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [] make test
• [] fullsync
• [] Other test (please specify)

Test Configuration:

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

• [] My code follows the style guidelines of this project
• [] I have performed a self-review of my code
• [] I have commented my code, particularly in hard-to-understand areas
• [] I have made corresponding changes to the documentation
• [] My changes generate no new warnings
• [] I have added tests that prove my fix is effective or that my feature works
• [] New and existing unit tests pass locally with my changes
• [] Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

Merging #3492 (e1299ce) into master (91fd545) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3492   +/-   ##
=======================================
  Coverage   75.40%   75.40%           
=======================================
  Files         245      245           
  Lines       22699    22699           
=======================================
  Hits        17117    17117           
  Misses       4656     4656           
  Partials      926      926           

Impacted Files	Coverage Δ
config/config.go	85.29% <ø> (ø)
blockchain/filedao/testing.go	59.71% <100.00%> (ø)
p2p/agent.go	77.85% <100.00%> (ø)
server/itx/heartbeat.go	78.43% <100.00%> (ø)

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