feat(rpc): rpc query contract code deployed

[ailisp]

Address #1712,
also, add a dump_code command to state-viewer, so we can dump wasm file given account id, from node that doesn't yet have this rpc, e.g. testnet/mainnet:

nearcore (query-view-code) target/debug/state-viewer dump_code --account 1.test.near
Dec 08 17:48:01.772  INFO near: Opening store database at "/home/bo/.near/data"    
Dec 08 17:48:01.911  INFO runtime: Tracking shards: {}    
Dump contract of account 1.test.near into file output.wasm
nearcore (query-view-code) ls
ATTRIBUTIONS.md     CODEOWNERS         Dockerfile          METRICS.md   runtime         tests
Cargo.lock          config3601.json    Dockerfile.nightly  neard        rustfmt.toml    test-utils
Cargo.toml          configmaster.json  docs                nightly      rust-toolchain  tools
chain               CONTRIBUTING.md    genesis-tools       output.wasm  scripts         utils
codecov.yml         core               LICENSE             pytest       SECURITY.md
CODE_OF_CONDUCT.md  deny.toml          Makefile            README.md    target
nearcore (query-view-code) base64 < output.wasm 
47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=

Test Plan

~ http post http://localhost:3030 jsonrpc=2.0 id=dontcare method=query params:='{"request_type":"view_code","finality":"final","account_id":"test.near"}'
HTTP/1.1 200 OK
content-length: 155
content-type: application/json
date: Tue, 08 Dec 2020 23:05:36 GMT

{
    "error": {
        "code": -32000,
        "data": "contract code of account test.near does not exist while viewing",
        "message": "Server error"
    },
    "id": "dontcare",
    "jsonrpc": "2.0"
}

~ http post http://localhost:3030 jsonrpc=2.0 id=dontcare method=query params:='{"request_type":"view_code","finality":"final","account_id":"1.test.near"}'
HTTP/1.1 200 OK
content-length: 240
content-type: application/json
date: Tue, 08 Dec 2020 23:05:43 GMT

{
    "id": "dontcare",
    "jsonrpc": "2.0",
    "result": {
        "block_hash": "3mZUK6DnPUnGSKr7LdU56pNRd2vuMCsnWQQpP1qMFXnH",
        "block_height": 41020,
        "code_base64": "47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=",
        "hash": "7KoFshMQkdyo5iTx8P2LbLu9jQpxRn24d27FrKShNVXs"
    }
}

and also nightly ci test_upload_contract_testnet

[bowenwang1996]

Can we add a sanity test to make sure that it works? Also this query maybe expensive if the contract code is large @frol

[frol]

LGTM! I left a few nits which you may ignore and merge as is, I only want us to be on the same page in terms of the reasoning we apply to the order of enum variants and From impls.

[frol]

Also this query maybe expensive if the contract code is large

I expect it to be on par with serving static files over HTTP (like Nginx does), which is usually bound by the network bandwidth rather than by the trie lookup, disk read, or memory read (borsh deserialization). Thus, I don't expect it to be more expensive than view_account query.

[ailisp]

@evgenykuzyakov can you review to unblock this PR?

[mikedotexe]

Let's please let @thisisjoshford know when we add new routes/endpoints so we can update the docs :)

[frol]

@mikedotexe I even submitted a PR: near/docs#562 😄

[mikedotexe]

@mikedotexe I even submitted a PR: near/docs#562 😄

My man! Thanks, Frol, on top of things as always. I searched for "view_code" in the Issues and didn't see it. I'll close mine. Thanks!