Resolve "Add a new `scord-control` CMake target"

This MR reorganizes the code so that a secondary scord-ctl daemon is built. Since a lot of the code is shared between scord and scord-ctl, it restructures the code structure and the CMake targets so that we can reuse as much as possible. In short, the following changes have been made:

• The source code for the scord daemon now has its own directory in src/scord
• A new scord-ctl target is added for the new daemon that lives in src/scord-ctl
• Library code now lives under the lib directory since api seemed ambiguous
• Public rpc definitions now live in src/lib/rpcs/
• Private rpc definitions for each daemon now live in src/scord/rpcs/ and src/scord-ctl/rpcs/, respectively
• config, logger, and network code now live under the common directory

Closes #9 (closed)