WiP: Verify that previous ATX points to correct ATX when handling incoming ATXs

[fasmat]

Motivation

Fixes GHSA-jcqq-g64v-gcm7

Description

• The Previous ATX is now verified to be from the same NodeID
  • if it is not it is a syntactic invalidity, the ATX is discarded and the peer that broadcasted the ATX will be dropped
• The activation.Handler now marks a NodeID as malicious if it produces two ATXs pointing to the same previous ATX
• A new malfeasance proof type was added that proofs that two different ATXs by the same smesher point to the same previous ATX
• Node can now be instructed to verify existing ATXs in the DB which will create and broadcast malfeasance proofs for every ATX that was found to be invalid, but no existing malfeasance proof is available
  • TODO: add command line flag that needs to be set to run this code explicitly
  • TODO: store progress in local DB instead of starting from the beginning every time

Test Plan

• tests were added for the new behaviour
• existing tests where updated where needed

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed
• Update changelog as needed

[fasmat]

superseded by #27