Breakout dependency sets into extras, establish a better pattern for adapters with missing imports

[timkpaine]

We haven't yet decided whether we want to push for adapters to all be part of csp proper, or if we want/expect adapters to be maintained independently. Regardless, we currently have C++-based parquet and kafka adapters, python-based db, csv, perspective, websocket, symphony, and slack adapters, with plans for C++-based redis, andwebsocket adapters, so it seems likely that we will have a reliance on lots of python libraries.

We will want to establish a (better) pattern for optional dependency sets, at the very least moving optional dependencies to their own extras blocks in pyproject.toml, and having a more graceful handling at runtime when dependencies are missing.