GC-BUG: Execution aborts while collecting old generation when using `free_all_kore_mem` in a few tests.

We observed that, while the new implementation of free_all_kore_mem looks more accurate from what it's supposed to do, we're now experiencing a segmentation fault when collecting the old generation in kore_collect.

The reason seems to be that the oldspace allocation_ptr is points to a memory position after the end of the oldspace, and thus, we can't correctly collect it. It's still uncertain why this happens, and the error seems to happen non-deterministically, probably because the program is executed using a pool of threads that (apparently) randomly switch threads during the execution of the program.

For now, the short-term solution is to not call munmap_arena_and_reset on the oldspace inside the free_all_kore_mem function, but we have to take a look into this issue GC issue later.

Start by reproducing the segmentation fault in the tests that use free_all_kore_mem, focusing on kore_collect and the oldspace allocation_ptr. Read the interactions between free_all_kore_mem and munmap_arena_and_reset, including the threaded execution context. Done means old-generation collection no longer aborts nondeterministically while preserving correct oldspace cleanup.