Calculate an RMSE for vertical profiles.

Starting point: model fields from $BASE_MODEL and $OTHER_MODEL that conatin pressure levels as vertical coordinate, lat and lon as spatial coordinates and a time coordinate.
This requires a new recipe and changes to the vertical_line_plotting operator to allow plotting of a vertical profile without a sequence coordinate as the time coordinate is not contained when calculating RMSE with scores.
It requires changes to handle scalar sequence coordinates.
It requires matching XARRAY and Iris dimension matching.

• Calculate a single profile RMSE by calculating RMSE on each pressure level across the spatial and the time coordinates.
• Calculate a profile for RMSE for each time point
• dimension matching between XARRAY and Iris
• include time aggregation period into plot title and file name
• generate vertical profile section udner verification in rose gui
• develop loader functionality
• enable switch for users to switch between time aggregated across single case study and rmse for evevry time step
• enable rmse profiles for model levels
• enable aggregation across case studies for by hour, lead time, validity time
• enable for ensemble capability