feat: implement flashblocks monitoring

[0x416e746f6e]

implement flashblocks monitoring:

• read from public stream + individual builder streams
• compare the flashblocks produced by all
  • detect mismatches
• detect if the stream has flashblock gaps
• compare captured flashblocks with canonical blocks
  • detect if there were flashblocks that were produced but were not added to the blocks

[avalonche]

shouldn't we detect inconsistent flashblocks at the end when the canonical block come through? it looks like we are comparing at every event and there will be a lot of mismatches just from latency differences and not be an useful measure.
e.g.
builder flashblock 2 comes in at 450 ms -> compares with last public flashblock (flashblock 1 -> mismatch)
public flashblock 2 comes in at 500 ms

[0x416e746f6e]

detectInconsistentFlashblocks compares payload id and index first. if they are not the same, not further comparison is made. that guarantees no false positives.

the most important part of the check if the check of the streams b/w individual builders (b/c the public one is anyway the same as one of the builders), and the latency to the builders is pretty much the same.

if we really-really want to compare 100% of all flashblock streams, we'd have to keep the history of each of them, and then implement some logic that would prevent that history from exploding. I left it out for the future for now.