Add 'write version' to EmulateRequestModel

[stanislav-tkach]

The write version is needed to correctly trace transactions because we need the exact state of the accounts.

Related to https://github.com/neonlabsorg/tracer-api/pull/67.

[Deniskore]

IMO, write_version should be passed as a parameter to the functions, not to the builder of the client.
What do you think @stanislav-tkach @andreisilviudragnea ?

[stanislav-tkach]

I though that the write version value is similar to a slot one that is already passed to the client constructor. I'm OK with both approaches, but I have a feeling that passing it as a parameter to function will be more verbose.

[andreisilviudragnea]

@Deniskore The dyn rpc::Rpc client returned by pub async fn build_rpc_client( state: &NeonApiState, slot: Option<u64>, write_version: Option<u64>, ) -> Result<Arc<dyn rpc::Rpc>, NeonError> is a request-scoped value.

In the case of debug_TraceTransaction, it is a CallDbClient value, which associates the tracer_db: TracerDb with a slot and an optional tx_index_in_block.

Both CallDbClient and Solana RpcClient need to implement the async fn get_account(&self, key: &Pubkey) -> ClientResult<Account>; method, which is the main method of the Rpc trait. This Rpc trait hides the source of the account state from the rest of the implementation (either ClickHouse or Solana RPC), so it is ok the way it is used now.