Minecraft singleplayer segfaults on RVVM framebuffer recycle

[LekKit]

Symptoms

• DisplayManager (Owned by client thread) doesn't give up Framebuffer references before the server thread destroys the machine
• Recent RVVM JNI bindings cause the framebuffer to be recycled immediately
• Crash on access to recycled framebuffer VMA from Java side via a still-living ByteBuffer

Solutions

Improve RVVM JNI framebuffer state recycling logic (Instead of freeing on RVVM side, implement cleaner callback in Direct ByteBuffer handed off to Java code?)

@Kamillaova do you perhaps have a good idea how to implement direct ByteBuffer cleanup callback into JNI C side?