Start abstracting dfi into it's own lib

[prasannavl]

Summary

• This PR renames masternodes/ to dfi/ in an effort to start abstracting dfi into it's own lib
• Later items to move are miner, PoS, etc which are still remnants.
• The outer rename facilitates all further changes to be small and no branches off separately disrupting parallel work or deviations from release mainline channels.
• Also to note: This is mostly automated with a few careful opt-ins around the tooling to just address bare essentials.

Implications

• Storage

  • Database reindex required
  • Database reindex optional
  • Database reindex not required
  • None

• Consensus

  • Network upgrade required
  • Includes backward compatible changes
  • Includes consensus workarounds
  • Includes consensus refactors
  • None