parity-clib: async C bindings to RPC requests + subscribe/unsubscribe to websocket events (#9920)

* feat(parity-clib asynchronous rpc queries)

* feat(seperate bindings for ws and rpc)

* Subscribing to websockets for the full-client works

* feat(c binding unsubscribe_from_websocket)

* fix(tests): tweak CMake build config

* Enforce C+11

* refactor(parity-cpp-example) : `cpp:ify`

* fix(typedefs) : revert typedefs parity-clib

* docs(nits)

* fix(simplify websocket_unsubscribe)

* refactor(cpp example) : more subscriptions

* fix(callback type) : address grumbles on callback

* Use it the example to avoid using global variables

* docs(nits) - don't mention `arc`

* fix(jni bindings): fix compile errors

* feat(java example and updated java bindings)

* fix(java example) : run both full and light client

* fix(Java shutdown) : unsubscribe to sessions

Forgot to pass the JNIEnv environment since it is an instance method

* feat(return valid JString)

* Remove Java dependency by constructing a valid Java String in the callback

* fix(logger) : remove `rpc` trace log

* fix(format)

* fix(parity-clib): remove needless callback `type`

* fix(parity-clib-examples) : update examples

* `cpp` example pass in a struct instead to determines `callback kind`
* `java` add a instance variable the class `Callback` to determine `callback kind`

* fix(review comments): docs and format

* Update parity-clib/src/java.rs

Co-Authored-By: niklasad1 <niklasadolfsson1@gmail.com>

* fix(bad merge + spelling)

* fix(move examples to parity-clib/examples)

rpc/src/lib.rs

@@ -108,6 +108,7 @@ pub mod v1;
 
 pub mod tests;
 
+pub use jsonrpc_core::{FutureOutput, FutureResult, FutureResponse, FutureRpcResult};
 pub use jsonrpc_pubsub::Session as PubSubSession;
 pub use ipc::{Server as IpcServer, MetaExtractor as IpcMetaExtractor, RequestContext as IpcRequestContext};
 pub use http::{