Kill provder

[Sriep]

The owner or other selected user should be able to kill a provider. This can use common code associated with a new embedded object (Provider or Killable)

• For each provider type, miner, sharder, blobber, validator and authoriser, we need a new kill_? transaction. This will set a new Killed flag in the provider object stored in the MPT and mirrored in the event database.
• If a provider is flagged as killed it will fail all validation to take on new provider commitments. It will also not be provided with any rewards or other paymetns.
• Killing a provider down is irreversible.
• There is a partial implementation for miners and sharders which can be copied and updated to work the new killed flag https://github.com/0chain/0chain/issues/499.
• For an overview see https://github.com/0chain/0chain/issues/1040.