Fix major basins behavior

[simone-silvestri]

The choice of major basins is performed on main, on an extended grid that is used to compute the connectivity in case of a Periodic direction. It might be, therefore, that large basins such as the Caspian sea are repeated within the extended grid, and are removed from the extended grid without changing the interior of the bottom height which is what we actually want to mask out.

In this PR we still compute the connectivity (the labels) using an extended grid, but we rank the basins only on the labels in the interior of the grid, correcting the behavior of major_basins.
For example the output of this script:

grid = TripolarGrid(size = (360, 180, 1), z = (-5000, 0))
bottom_fields = [Array(interior(regrid_bathymetry(grid; minimum_depth = 10,  major_basins = i), :, :, 1)) for i in 1:6]
diffs = [bottom_fields[i] .- bottom_fields[i+1] for i in 1:5]

fig = Figure(size = (800, 1400), fontsize = 14)

for i in 1:5
    ax = Axis(fig[i, 1], title = "major_basins = $(i+1) − $i", aspect = DataAspect())
    heatmap!(ax, diffs[i]; colorrange = (-0.001, 0.001))
    hidedecorations!(ax)
end

on main:

on this PR:

cc @taimoorsohail

[glwagner]

Did you know that the Caspian sea is 1000m deep and the remnant of an ancient ocean? Maybe you should include it in your bathymetry.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.01%. Comparing base (41f27e7) to head (3aa29cd).

Files with missing lines	Patch %	Lines
src/Bathymetry.jl	0.00%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #708      +/-   ##
==========================================
- Coverage   41.06%   41.01%   -0.06%     
==========================================
  Files          57       57              
  Lines        3156     3160       +4     
==========================================
  Hits         1296     1296              
- Misses       1860     1864       +4     

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