Refactor dirty block management with ConcurrentHashMap and version bump

[twisti-dev]

This pull request includes a version bump and an internal improvement to how dirty blocks are tracked in the BlockPdcManager. The most significant change is the replacement of a custom mutable set with a thread-safe concurrent set for managing dirty blocks, which increases safety in concurrent environments.

Version update:

• Incremented the project version in gradle.properties from 1.21.11-2.70.0 to 1.21.11-2.70.1.

Thread safety improvement:

• Replaced the use of mutableObjectSetOf with ConcurrentHashMap.newKeySet for the dirtyBlocks set in BlockPdcManager, ensuring thread-safe access and modification.

[Copilot]

Pull request overview

This PR bumps the project version and refactors internal “dirty block” tracking in the Bukkit server implementation to use a thread-safe concurrent set, improving safety when dirty tracking is accessed from multiple coroutines/threads.

Changes:

• Bumped version in gradle.properties from 1.21.11-2.70.0 to 1.21.11-2.70.1.
• Replaced mutableObjectSetOf with ConcurrentHashMap.newKeySet() for BlockPdcManager.dirtyBlocks to make dirty tracking thread-safe.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
surf-api-bukkit/surf-api-bukkit-server/src/main/kotlin/dev/slne/surf/surfapi/bukkit/server/impl/pdc/block/BlockPdcManager.kt	Switches dirty block tracking to a concurrent set and removes the custom fastutil set usage.
gradle.properties	Applies the patch-level version bump for the release containing the internal refactor.