eth_getRawBlockByNumber for RPC API (part 1, issue 9057)

[lamafab]

Hello

This PR contains (some) changes requested by issue #9057. The issue also requested a eth_submitRawBlock implementation. This feature has not been written yet -> I will follow up with that in a separate PR.

(The original request specified the parity_ prefix instead of eth_. I assume that was an error and eth_ is correct here?)

Changes

• eth_getRawBlockByNumber API for both the full and light client. This endpoint returns the raw block in RLP form, no extras included (non-Rich). The return value is tested on the official Ethereum test cases in BlockchainTests/bcGasPricerTest/RPC_API_Test (the json file contains a "rlp" field).
• To avoid duplicating code, the rich_block method on EthClient in both the full and light client has been split into encoded_block and rich_block (rich_block calling encoded_block from within).

Todo

• As I already mentioned, eth_submitRawBlock will follow up in a separate RP.
• While the endpoint does accept a include_txs: boolparameter, it currently does not do anything (transactions are included, the default). The rpc::v1::types::Block type can easily exclude transactions, the ethcore::types::encoded::Block type however is a little more complex as it only contains the raw bytes. I could use BlockView to find the transactions and cut those out from the final form. I will do that, soon (unless someone can recommend a different way of doing this?). Should this parameter be removed for now?

Open questions

• Should there be a similar endpoint for eth_getBlockByHash, i.e. eth_getRawBlockByHash?
• While I did test the changes for the light client by hand, there do not seem to be any automated tests for it. Did I miss those somewhere? By searching the code base it seems to only test the full client RPC interface.

[parity-cla-bot]

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Many thanks,

Parity Technologies CLA Bot

[seunlanlege]

already implemented in #10609