Implement SST Anomaly functionality

### Are there any linked Issues or Pull Requests?

_No response_

### Brief description

Functionality that is used and required from the UM is the ability to apply an SST anomaly to the ancillary updated SST. The main driver of this ticket is to be able to replicate the AMIP SST+4K experiment, where by the SST is increased by 4K in order to measure climate feedback.

There are potentially 3 different methods to this. What is common across the 3 methods is that an adjustement is made to the SST field (sea tile of tile_temperature) based on a given input. Only the SST on open sea is updated, e.g. no sea ice where SST is fixed to 0degC.

1. Apply a single value at all open sea points
1. Apply a value from a given anomaly ancillary field
1. Supply an SST climatology and calculate anomaly from existing SST, and apply this field

This issue will look into implementing the first of these options which can be done by a simple namelist setting. The remaining cases would require the anomaly field to be retained in the checkpoint file.

### Further details of the issue.

_No response_