Clean up summary API usage

[kmcginnes]

While investigating a user's schema sync issue I noticed some code that could use some cleaning up.

• Calls with mode=detailed but doesn't use extra fields
• Does not validate response structure
• Performs unchecked property access on response

graph-explorer/packages/graph-explorer/src/connector/gremlin/gremlinExplorer.ts

Lines 47 to 69 in b099623

	async function fetchSummary(
	connection: NormalizedConnection,
	featureFlags: FeatureFlags,
	options?: RequestInit
	) {
	try {
	const response = await fetchDatabaseRequest(
	connection,
	featureFlags,
	`${connection.url}/pg/statistics/summary?mode=detailed`,
	{
	method: "GET",
	...options,
	}
	);
	return response.payload.graphSummary as GraphSummary;
	} catch (error) {
	logger.error(
	"[Gremlin Explorer] Failed to gather summary statistics",
	error
	);
	}
	}