Tracking: Support invalidating and reconsidering blocks in the NonFinalizedState via RPC methods

[arya2]

Motivation

This would be useful for testing forks and chain reorganizations, it was mentioned in the forums as a requirement for dex support and in the Regtest tracking issue.

See this comment for more information about the motivation.

Design

Add invalidate()/reconsider_block() methods to the NonFinalizedState, accept a new channel in write_blocks_from_channels() running in the the block write task (or refactor the existing channels into a single channel receiving an enum), add StateService Request variants for invalidating/reconsidering blocks, and add the invalidate()/reconsiderblock() RPC methods that call the StateService with the new Request variants.

Implementation Plan:

• Add a field to the NonFinalizedState for invalidated blocks #8840
• Add an invalidate_block() method to the NonFinalizedState for removing a block and its descendents #8841
• Add an reconsider_block() method to the NonFinalizedState for validating/committing a previously invalidated block and its invalidated descendents #8842
• Accept a new channel in (or refactor the existing channels into a single channel where the message type is an enum) #8843
  • Call the new NonFinalizedState methods when the block write task receives a message to invalidate or reconsider a block #8844
• Add a InvalidateBlock StateService Request variant which sends a message to the block write task #8845
• Add a ReconsiderBlock StateService Request variant which sends a message to the block write task #8846
• Add an invalidate() RPC method #8847
• Add a reconsiderblock() RPC method #8848