Implement offline tallying and online validation for private vote plans

[mzabaluev]

The tallying process for private vote plans is computationally intensive. It makes sense to perform it outside of the ledger implementation and only do validation in the node with computed results sent as part of the tallying transaction.

Work to do

• Validation function in chain-vote: Implement validation function in chain-vote chain-libs#515
• Change the private tally transaction to include results computed offline and use the validation function to validate on-ledger: Change private tally transaction to carry results computed offline #2971
• Offline computation of the tally results in jcli: Offline tallying in CLI #2972
• Update tests: Update tests for offline tallying of private voting #2973