Reduce Go import burden

[griffin]

Hello, I'm interested in using this package to benchmark some internal systems, but the repo as a whole is pretty difficult to import because it is one giant Go module with imports of many database libraries we have pinned internally.

Would the maintainers be open to splitting the code into three types of modules?

• One a the base of the repository which would be used to import anything in the pkg directory
• One for each db, which would just include the basic client
• One for the CLI for go install-ing, which would import all of the clients in the db, which would serve as the default distribution.