Initial tests of unequal sized images

[kmdeck]

Purpose

Adds tests for cases where images do not have equal number of pixels in each dimension.

Our current code seems to run fine, so this only adds tests.

To-do

carry out a test with a dataset?
rebase and merge

Content

updates tests to have the case where nx is not equal to ny

Review checklist

I have:

• followed the codebase contribution guide: https://clima.github.io/ClimateMachine.jl/latest/Contributing/
• followed the style guide: https://clima.github.io/ClimateMachine.jl/latest/DevDocs/CodeStyle/
• followed the documentation policy: https://github.com/CliMA/policies/wiki/Documentation-Policy
• checked that this PR does not duplicate an open PR.

In the Content, I have included

• relevant unit tests, and integration tests,
• appropriate docstrings on all functions, structs, and modules, and included relevant documentation.

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• I have read and checked the items on the review checklist.

[kmdeck]

we assume this in sampling says @sandreza