Remove block entities on server thread

[HaHaWTH]

Overview

Fix unsafe async block entity removal in Paperweight chunk write adapters.

Description

This PR fixes an issue where PaperweightGetBlocks#internalCall could remove block entities directly while running on FAWE queue worker threads.

Previously, when an edit replaced blocks in a chunk, existing block entities were removed immediately during chunk processing via LevelChunk#removeBlockEntity or the Paper beacon removal path. As the backing blockEntities map is not designed for concurrent writes, this can cause backing map corruption.

Existing Issues

After removing BEs in the final sync tasks, this may spam logs like Block entity A @ BlockPos state Block{B}[facing=north,type=single,waterlogged=false] invalid for ticking: as the removal happens after the chunk section swap.

I am not sure whether the preferred long-term fix is to:

• keep this approach as the minimal thread-safety fix,
• move block entity removal into an earlier synchronous phase before the section swap,

Feedback would be appreciated here, especially around the expected ordering between block entity removal, beacon deactivation events, and the chunk section replacement performed by internalCall.

Submitter Checklist

• Make sure you are opening from a topic branch (/feature/fix/docs/ branch (right side)) and not your main branch.
• Ensure that the pull request title represents the desired changelog entry.
• New public fields and methods are annotated with @since TODO.
• I read and followed the contribution guidelines.

[SirYwell]

Relevant: #3152

[SirYwell]

Also #3543 I think

[HaHaWTH]

Workaround for log spam: set the remove field through reflection inside the loop, this should be a minimal fix

[HaHaWTH]

Reference for event contract: BlockEntity removal should happen after the event