Add tests of entity conflict summary table

[matthew-white]

The entity conflict summary table was added in #894. However, that PR included a limited number of tests. This issue is to add more tests of the table. The following comment lists cases to include in those tests: getodk/central#529 (comment)

[matthew-white]

Here's one piece of code that I'm pretty sure isn't working right now:

central-frontend/src/components/entity/conflict-table.vue

Lines 142 to 151 in 00d8409

	// Check for properties that are in allReceived but not dataset.properties.
	const expectedCount = allReceived.has('label')
	? allReceived.size - 1
	: allReceived.size;
	if (result.length !== expectedCount) {
	const propertySet = new Set(dataset.properties);
	for (const name of allReceived) {
	if (name !== 'label' && !propertySet.has(name)) result.push(name);
	}
	}

Specifically, dataset.properties is an array of objects, not an array of names, so line 147 should probably be something like:

const propertySet = new Set(dataset.properties.map(({ name }) => name));