Better support for multiple tablist add/remove

[pop4959]

The Minecraft protocol supports adding/removing multiple entries from the tab list in a single packet (see Player Info Update and Player Info Remove).

Currently, while Velocity does have an addEntries method on its TabList, the method currently processes each entry individually regardless of what entries are being updated.

Velocity/api/src/main/java/com/velocitypowered/api/proxy/player/TabList.java

Lines 53 to 57 in a078053

	default void addEntries(Iterable<TabListEntry> entries) {
	for (TabListEntry entry : entries) {
	addEntry(entry);
	}
	}

There are no subclasses of TabList which override this default behavior, meaning each individual tab list entry sends a separate packet, which is undesirable.

Similarly, removeEntry exists, but in this case there are no corresponding removeEntries methods, even though removing multiple entries is also supported (and trivial).

This PR attempts to address this by refactoring the existing code from addEntry to addEntries in VelocityTabList, where addEntries now handles batching tab list modifications into the least number of packets possible. It is not possible (to my knowledge, I'm happy to be corrected) to combine modifications that contain varying length player actions, as a restriction imposed by the protocol, since the actions must prefix the list of entries being updated. As a result, the existing addEntry method can simply delegate to addEntries passing only one entry. The removeEntries implementation is pretty straightforward, my goal there was simply to mirror the same kinds of overloads as addEntries has, and keep the same behavior of returning all of the removed TabListEntry instances.