Added qml tests for the vertex editor geometry tool

[kaustuvpokharel]

This pr adds a qml test file for the vertex editor tool. The vertex model itself is already covered in test_vertexmodel.cpp, so this does not retest that. It focuses on the tool layer around it: init wiring, applyChanges and the autoSave branch, cancel, remove, and undo.

The tool reads a few objects from its parent scope in the app (qfieldSettings, coordinateLocator, etc). I provide them in the test the same way tst_featureForm.qml does, as plain in-scope items. mapSettings is a real MapSettings set to the Fields layer CRS so the vertex model transform is a no-op. Tests run against the existing Fields (polygon) and Tracks (line) features in test_bees.qgz, and never commit, the edits go to the layer edit buffer and are rolled back after each test so the shared data stays clean.

canvasClicked is left out on purpose. It turns a screen point into a map coordinate through mapSettings.screenToCoordinate, which only means something with a real rendered canvas. Without one the screen to map math is meaningless, so a click test there would just assert made up numbers. That path fits an integration (spix) test better, is what I thought, if we need it.
I did not test the remove-down-to-minimum case. The polygon has 12 real vertices so it would take about 8 removals to trip canRemoveVertex false, which could endup fragile. Instead canRemoveVertex is checked from both sides: true on a removable vertex in edit mode, false outside edit mode. That covers the guard without exhausting the ring. I also left out the save-failure toast branch. Forcing featureModel.save() to return false means making the layer non-editable mid-operation, which is fragile and risks leaving the shared layer dirty. It is a thin error branch and not worth the check, let me know if you think otherwise @nirvn . All tests pass es locally.

[qfield-fairy]

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