refactor(api, blocking)!: add new trait Client, apply to blocking

- add new APIs: `TransactionApi`, `AddressesApi`, `BlocksApi` and
  `FeeEstimatesApi`
- add new `trait Client` with minimal HTTP behaviors: `request`, `send`
  and `deserialize_{decodable|json|str}` methods.
- apply new APIs to `BlockingClient`, create new `handler` to build
  request and send with minreq HTTP client.

Author: oleonardolima

Cargo.toml

@@ -23,6 +23,7 @@ hex = { package = "hex-conservative", version = "0.2" }
 log = "^0.4"
 minreq = { version = "2.11.0", features = ["json-using-serde"], optional = true }
 reqwest = { version = "0.11", optional = true, default-features = false, features = ["json"] }
+serde_json = { version = "1.0.127" }
 
 [dev-dependencies]
 serde_json = "1.0"