If the same chunk is set into multiple different places in the world, the chunk's position is no longer able to be relied on, because it will have the position of the last place it was set. This results in chunks not getting sent correctly when the same chunk is set in multiple places.
This avoids the bug by using known valid coordinates (using chunk hashes) to establish the real coordinates, and also adds an assert to notify developers should they unintentionally set a duplicate chunk by mistake.
- Doesn't need to be pre-populated with biomes prior to calculating the heatmap - now population of biomes is entirely dependent on the lookup function, improving consistency
- Uses an abstract class method for lookup instead of callback (use anonymous class instead)
- Faster because the heatmap is directly populated with biomes instead of biome IDs, removing an unnecessary lookup.
- Removed `Server->getScheduler()`. All plugins now have their own scheduler which is accessible using `Plugin->getScheduler()`. Aside from being syntactically more concise and pleasant, this also allows much more effective management of tasks when plugins are disabled.
- Removed `PluginTask` class. Before this PR it was necessary for plugin tasks to descend from `PluginTask` to ensure that the server could clean them up correctly on plugin disable. This is no longer necessary, so the `PluginTask` class has been removed. Plugins may now utilize the `Task` class as a base if they like.
- Added `Server->getAsyncPool()`. Since the global scheduler does not exist any more, it does not manage the server's `AsyncPool` any more. Additionally, `ServerScheduler` was previously bloated by a lot of `AsyncTask` related methods, which are now not necessary because direct access to `AsyncPool` is granted instead.
- `ServerScheduler`:
- `ServerScheduler` has been renamed to `TaskScheduler` since it is now a general-purpose task scheduler which is non-dependent on the user. This allows much greater flexibility and also makes it possible to unit-test.
- All `AsyncTask`/`AsyncPool` related methods have been removed - the task scheduler does not manage the async pool anymore.
- Calls to `Server->getScheduler()->scheduleAsyncTask()` should be replaced with `Server->getAsyncPool()->submitTask()`.
- Calls to `Server->getScheduler()->scheduleAsyncTaskToWorker()` should be replaced with and `Server->getAsyncPool()->submitTaskToWorker()`.
## Backwards compatibility
This poses significant backwards compatibility breaks for any plugins utilizing Tasks or AsyncTasks. These breaks are described above, along with basic upgrade steps. The upgrade process is quite straightforward.
## Follow-up
A large part of the goal with this pull request is to modularize these parts of the code so that they can be reused and also unit-tested. I would like to remove the existing test set from TesterPlugin at some stage when the AsyncPool can operate without a Server.
Because of the above, I am considering making further backwards incompatible changes directly to `AsyncTask` to remove the `Server` parameters from `onCompletion()` and `onProgressUpdate()`. These shouldn't be too difficult to upgrade from and can be prepared for in advance.
