Consider simplifying pattern for waiting for empty block in tests

[dima74]

Is there a good way to avoid this repeating pattern? At least for the block immediately following the genesis block, I think NetworkBuilder::start_blocking could imply that commit

Pattern:

// Waiting for empty block to be committed
std::thread::sleep(network.pipeline_time());

See https://github.com/hyperledger-iroha/iroha/pull/5320/commits/6fb19964009c2133c80457e0e30d6b36d7d9f7f8

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Originally posted by @s8sato in https://github.com/hyperledger-iroha/iroha/pull/5320#discussion_r1971149320

[0x009922]

NetworkPeer already provides a precise API exactly for this case: events, once, and once_block. For example:

https://github.com/hyperledger-iroha/iroha/blob/84c117a62983ec7c771353e90eac1f4c6da7edf9/crates/iroha/tests/extra_functional/restart_peer.rs#L44-L47