Fix/rpc request serde

[whalelephant]

Motivation

Closes #1369 without introducing new dependencies with jsonrpc-* crates.

There is an issue with parsing numerical value with json rpc id field. The work around implemented is to first parse into serde_json::Value as suggested here.

Another PR to the temp dependency json-rpc-type fixes the issue of how serde_json::Value string deserialization requires escaping and cannot therefore be cast to a borrowed str type.

Test Plan

 curl -s -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"latestblockheight","params":[],"id":"1"}' localhost:3032
 
 curl -s -H "Content-Type: application/json" -X POST --data '{"jsonrpc":"2.0","method":"latestblockheight","params":[],"id":1}' localhost:3032

Related PRs

#1496
#1537

[ljedrz]

The CI doesn't want to start; I'll try reopening, it sometimes helps.

[ljedrz]

Did it get stuck again? Let me retry.

[ljedrz]

LGTM 👍

[raychu86]

LGTM