Figure out if server-side updates are already grouped by table

[RReverser]

Here

com.clockworklabs.spacetimedbsdk/src/SpacetimeDBClient.cs

Lines 476 to 478 in 9696cd3

	// TODO: is there any guarantee that transaction update contains each table only once, aka updates are already grouped by table?
	// If so, we could simplify this and other methods by moving the dictionary inside the main loop and using only the primary key as key.
	var primaryKeyChanges = new Dictionary<(IRemoteTableHandle table, object primaryKeyValue), DbOp>();

and in other places we could simplify quite a bit of code if we can assume that database updates / transaction updates already have updates grouped and deduplicated by table, but it's currently not clear if it's something we can rely on.