rm weighted_dss_slab

[juliasloan25]

Purpose

We have been using a function weighted_dss_slab! that loops over each Field in the state FieldVector, retrieves the dss buffer from the cache, and then calls CC.Spaces.weighted_dss!(field, buffer). We can delete this function if we extend weighted_dss! to be extended for FieldVectors in ClimaCore, which will be useful for ClimaAtmos as well.

closes #396

To-do

• extend ClimaCore function extend weighted_dss for FieldVector ClimaCore.jl#2000
• release ClimaCore (currently 0.14.16)
• update ClimaCoupler to use new interface
• update dss_buffer structure: create buffer for fieldvector so we have space for each field