Add unit tests for goal template types

[ACWalker]

This PR adds unit tests for the various goal template types, which helps address this issue #1686. I hope this will help to improve the robustness of the templates going forward.

For each goal template type, I have created a file containing the unit tests for that template type. I've tried to cover as many of the potential scenarios as possible, but there will definitely be some scenarios I haven't covered, this is just to get the ball rolling.

While writing these tests I have found some areas in the goal templates that we can refactor and improve, which I can address in subsequent PRs.

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[github-actions]

Bundle Stats — desktop-client

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static/js/indexeddb-main-thread-worker-e59fee74.js	13.5 kB	0%
static/js/resize-observer.js	18.37 kB	0%
static/js/BackgroundImage.js	122.29 kB	0%
static/js/AppliedFilters.js	27.56 kB	0%
static/js/usePreviewTransactions.js	790 B	0%
static/js/narrow.js	78.27 kB	0%
static/js/wide.js	277.35 kB	0%
static/js/ReportRouter.js	1.24 MB	0%
static/js/index.js	3.04 MB	0%

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kcab.worker.js	1.14 MB	0%

[MikesGlitch]

Amazing work!