Collect validation stats and report them to Slasher component

[SmaGMan]

During block validation, collect statistics on:

• which validators submitted valid block signatures
• which validators submitted invalid signatures

This data should then be sent to the slasher component for further processing.

Implementation suggestions:

• Report the statistics via a channel. A single channel can be used for multiple types of statistics, separated by an enum.
• Do not record the statistics immediately upon reaching 2/3+1 signatures weight. Instead, allow additional time to collect late signatures from validators who may be slightly behind. This prevents the issue where up to 1/3-1 validators are incorrectly marked as "lazy" just because their signatures arrived after consensus was reached. This additional time should be configurable, even 0.
• The slasher is a separate component and it's task spawned inside Node::run(). It should publish a Sender for the statistics channel, which other components can use to submit data.
• For the initial version, the slasher can simply export collected statistics to metrics for visualization and monitoring.