GHSA-3RCQ-39XP-7XJP ic-stable-structures vulnerable to BTreeMap memory leak when deallocating nodes with overflows

Impact When storing unbounded types in a BTreeMap, a node is represented as a linked list of "memory chunks". It was discovered recently that when we deallocate a node, in some cases only the first memory chunk is deallocated, and the rest of the memory chunks remain incorrectly allocated, causin...