Sync with PALEOboxes v0.22 / PALEOmodel v0.16 dimensions, coordinates changes

[sjdaines]

Reactions that create grids updated to use new approach to attach coordinates to dimensions.

Changes are backwards-compatible (ie work with old and new versions of PALEOboxes and PALEOmodel, except for MITgcm transport where changes to grid setup are too large.

Example of changes, from ReactionOceanTransportColumn setup_grid:

    # attach coordinates to grid for output visualisation etc
    if isdefined(PB, :set_coordinates!) # PALEOboxes >= 0.22
        PB.set_coordinates!(rj.domain.grid, "cells", ["zmid", "zlower", "zupper"])
    else
        empty!(rj.domain.grid.z_coords)
        push!(rj.domain.grid.z_coords, PB.FixedCoord("zmid", grid_vars.zmid, PB.get_variable(m, "zmid").attributes))
        push!(rj.domain.grid.z_coords, PB.FixedCoord("zlower", grid_vars.zlower, PB.get_variable(m, "zlower").attributes))
        push!(rj.domain.grid.z_coords, PB.FixedCoord("zupper", grid_vars.zupper, PB.get_variable(m, "zupper").attributes))
    end