fix(repo): Normalize cursor word length

[petertonysmith94]

Summary

• Normalised all the cursor word lengths to 6 to ensure consistent sorting behaviour (except the first element).
  • Example using [block_height].[tx index].[receipt index]
  • Before 123.2.1
  • After 123.000002.000001
• Added Testnet to the networks.
• Updated the message model to form a Cursor consistently with the rest of the application.