Schematic Cannon Memory Leak #10838

Description

When using the Schematic Cannon to build a schematic, a severe memory leak occurs. The server/game rapidly accumulates millions of BlockPos objects in heap memory during the placement, leading to high garbage collection latency, severe FPS drops and freezing. Eventually an OutOfMemoryError crash / disconnect. (DistantHorizons is the first victim) The game will not always forcefully shut down. Most of the time it shows as a "java.net.SocketException: Connection Reset" but after mining the schematic cannon the game get OOM errors show on screen.

Here are some screenshots from the profiler:

After 5 minutes:

After 10 minutes:

As you can see net.minecraft.core.BlockPos grows

Game Log

https://mclo.gs/1sjgrnK (OOM-crash) & https://mclo.gs/uY5h4ko (Softcrash)

Debug Information

1. Place a Schematic Cannon and insert a larger schematic.
2. Supply the cannon with necessary materials
3. Start the printing process.
4. Observe memory usage (e.g., via Spark profiler or VisualVM). heap memory usage rapidly climbs due to uncollected BlockPos references.