Decouple container management

[ayanchoudhary]

closes #169
This PR decouples container management logic from the docker client and creates an abstraction layer to allow for generic cr implementation. Currently has docker as the connected cr but will be swapped with containerd+buildkit in later commits

Tasks:

1. Decouple container management logic from docker client
2. Abstract container management logic to a shim layer
3. Add buildkit and containerd packages
4. Implement containerd implementation for shim
5. Integrate buildkit for handling image building