As a group, it was decided that we should not expose the attach/detach API to the public extensions API header until we have a concrete idea of what we'd like to do with regards to exposing the OpCtx to extensions.

Unfortunately, the PR that introduced these was merged before this decision was made see (https://github.com/10gen/mongo/commit/9e84005c9fdb9bf736a06ce452870e4c3d88c36b#diff-59d46c68dfab27e37ba4a9f0572ab1b2b8ac95d465d2a6ba473c011f1142e48a )

As part of this ticket, remove attach and detach from the API.