The separation between the BSON packages mostly exists to prevent import cycles, but otherwise doesn't make a lot of sense to users. Additionally, the separation between BSON packages requires that much more code is exported that otherwise doesn't need to be exported. For example, most functions on the the Copier type only need to be exported because they are used by code in the bson and mgocompat packages. Otherwise, there is no known use case for that type.

Definition of done:

• Move all exported symbols from the bsonrw package into the bson package.
• Update all dependent code in the Go driver to reference bson instead of bsonrw.
• Update all documentation in the Go driver to reference bson instead of bsonrw.