Fix Quit/Death message performance by building Notice asynchronous.

[vLuckyyy]

Note

This is mostly a MiniMessages performance issue.

Problem:
Spark profiler showed ticks exceeding 100ms with 150+ players online. The culprit was PlayerQuitMessageController using synchronous Notice#send() instead of Notice#sendAsync(), which blocked the main thread while broadcasting to all online players. JoinMessage already used Notice#sendAsync() for regular joins, but still used Notice#send() for first-time joins, plus it was sending two separate broadcasts per first-time player.

Solution:

• Changed QuitMessage to use Notice#sendAsync() (same as JoinMessage already did - That's why Spark only showed QuitMessage, not JoinMessage.)
• Fixed JoinMessage to send only one broadcast instead of two for first-time players
• Pre-allocated HashSet capacity in BukkitViewerProvider to avoid reallocations when iterating 150+ players

[gemini-code-assist]

Code Review

This pull request effectively addresses the performance issue with quit messages by switching to asynchronous sending. The consolidation of join messages is also a great improvement, reducing redundant broadcasts. My review includes a few suggestions to further enhance code conciseness and maintainability by using more modern Java features like ternary operators and streams. Overall, these are solid improvements to the codebase.