Ledger state validation (MS5.5)

[buddhisthead]

Description

Expose any errors detected by ledger state modules as validation errors

Intersect Milestone

MS5.5

Acceptance Criteria

• Verify no ledger errors in existing mainnet blocks
• Verify signalled failures in constructed bad Tx

Expected Deliverables

• Upgrades to ledger state derivation modules (see MS1) to report errors
• Test reports

[buddhisthead]

@shd Please assign to someone as you desire.

[shd]

This ticket has many sub-tickets, and all of them have typical info, so it's better provide one description here:

1. Collect all validation errors into ValidationError struct values, and have a list of them at the end of each message processing.

2. Check Intention enum in BlockInfo:
   a) If it is 'Apply', then work as usual, and errors are to be printed.

   b) If it is 'Verify', then no internal structures are to be updated, and the errors are to be sent to validation channel ('cardano.validation.account'), using ValidationStatus enum. For simplicity, only the first error is to be passed through the channel, although the implementation should collect all known errors, and have them in vector at the send moment.

   If no errors found, ValidationStatus::Go message is mandatory, so module must send always exactly one ValidationStatus message in 'Verify' mode.

   c) if both flags are set, then 'Apply' should take place if 'Verify' was successful (no errors) -- this may be implemented at later stage, if it is a complicated change; then a new ticket should be created, and info about that should be mentioned in the PR/this ticket.

All other functionality (like passing messages further) should work as usual.