Testground SDK for Nim

Quickstart: ```sh # Assuming testground is correctly setup git clone https://github.com/status-im/testground-nim-sdk.git cd testground-nim-sdk testground plan import --name demo --from examples/simple_tcp_ping testground run single --plan=demo --testcase=simple_tcp_ping --runner=local:docker --builder=docker:generic --instances=2 ``` This is not stable in any shape or form. Features: - [X] Basic communication with testground - [X] Logging - [X] Network configuration - [X] Signal, barrier - [X] PubSub - [X] Run configuration - [ ] Multiple scenario in a single plan - [ ] Metrics - [ ] ..