Add metrics

[unnawut]

Consolidating metrics requirements from various sources. Some of them are currently available but only because we're parsing it from logs and needs conversion to proper metrics.

• Count of calls to ethereum client (we already have per calling signature but not the total, which makes it hard to sum up)
• Count of deposits created (total and per token address)
• Count of blocks submitted feat: block queue metrics and stalled submission alarm #1649
• Count of txs submitted per token address excluding fee txs
• Count of txs submitted excluding fee transactions (txs submitted already exists but it includes fee txs)
• Count of utxos in utxoset (sampled at regular time intervals) - feat: add metrics: balance per currency, number of unspent outputs, number of addresses #1666
• Count of unique addresses owning at least 1 utxos (sampled at regular time intervals) - feat: add metrics: balance per currency, number of unspent outputs, number of addresses #1666
• Count of exit events
  • start exit
  • piggyback IFE
  • challenge exit
  • invalid exits
  • byzantine conditions
  • exit finalized
• Exit queues
  • Count of exits still under exit period, per exit queue
  • Count of exits ready to be processed, per exit queue
• Attempted gas price (currently available only in logs)
• Successful gas price (currently available only in logs)
• Childchain block number
  • Last submitted by child chain feat: block queue metrics and stalled submission alarm #1649
  • Last recognized by watcher/watcher_info
• Balance per token (currently count by utxos and therefore missing deposits) - feat: add metrics: balance per currency, number of unspent outputs, number of addresses #1666