Remove `thread` crate (#921) #899

Job	Run time
build all rust contracts	5m 51s
test eth-prover	4m 40s
test eth-client	7m 19s
test eth2-client	7m 25s
test eth2near/contract_wrapper	7m 2s
test eth2near/finality-update-verify	5m 46s
test eth2near/eth2-to-near-block-relay-rs	8m 9s
test eth2near/eth2-contract-init	6m 38s
test eth2near/eth_rpc_client	7m 20s
	1h 0m 10s

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