Clique createemptyblocks transition

[siladu]

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PR description

Create genesis config transitions:

  "config": {
    ...
    "clique": {
      "blockperiodseconds": 3,
      "epochlength": 30,
      "requesttimeoutseconds": 6,
      "createemptyblocks": true
    },
    "transitions": {
      "clique": [
        {
          "block": 3,
          "createemptyblocks": false
        }
      ]
    }
  },

Fixed Issue(s)

Fixes #6290

[fab-10]

Please rebase