The fact that the guarded-allocated memory blocks are all linked to the
static `membase` listbase is enough for LSAN to not detect them as
leaks.
So this commit adds a new (private) callback to clear the memlist, which
is only used in the destructor of the `MemLeakDetector` class.
Many thanks to @Sergey for identifying the root issue here.
Pull Request: https://projects.blender.org/blender/blender/pulls/110995
c5feb0cada