There was a data race inside `CoroutineGroup` because internal timer was
used from multiple threads in the methods `asyncWait()` and
`onCoroutineComplete()`. Changing `registerForeign()` to spawn to the
same `yield_context` fixes the problem because now the timer is accessed
only from the same coroutine which has an internal strand.
During debugging I also added websocket support for `request_gun` tool.
In this PR:
1 We create a golang grpc client to request data from rippled
2 We store the data into the specific place
3 Add unittests
4 Create build script, the build can be initiated by set conan option
`snapshot` being true.
Please ignore the grpc server part. It will be implemented in importing
tool.
