chore: tweak log levels and add logs

[yangby-cryptape]

• tweak log levels

  After light client reaches the latest block, then:

  • If it has N peers, copy prove state from peer will be output N-1 times for every block.
  • no check point is found will be output 1999 times per 2000 blocks.
    So, change levels for those logs to trace.

• add logs

  At present, if trace logs are enabled, only the block numbers are output when print difficulties distribution.

  So, print block hashes at function entry.