Adds tests for `Nbt*` objects correctly reporting their length.
Adds tests for `Nbt*` objects correctly reporting their length.

Signed-off-by: Aaron Jacobs <94eb18a3f3d75b115c91915c9ebacc4dd15c8941@gmail.com>

fenhl/hematite_server,PistonDevelopers/hematite_server,atheriel/hematite_server,toqueteos/hematite_server