Support for high-resolution LCT?

# ✨ Feature Request
I have previously found stripes of missing data when generating the land-sea mask at resolutions of 50 m and 10 m and fixed the issues with a branch on FCM at version 1. The problem still occurs in the latest version built from Git. I'm not sure whether this is actually a bug or whether specifying a larger padding width somewhere we solve the problem. As a starting point, I will replicate the old solution in a feature branch to see how much of it is required.

## Requirements
To avoid missing data in the land mask at high spatial resolution.

## Context
Generation of land cover at high spatial resolution.

Start by comparing the latest Git version with the earlier FCM version 1 solution referenced in the issue, then reproduce land-sea mask generation at 50 m and 10 m. Use the feature-branch replication to determine which parts are required; done means the high-resolution land mask contains no stripes of missing data.

Written by the indexing model from the issue text.