Describe the bug

MemoryConsumer::try_grow calls through to MemoryManager::can_grow_directly which determines the remaining space by performing self.pool_size - trk_total.

This can potentially underflow if the tracked memory exceeds the pool size, something for which there is no protection.

To Reproduce

#[test]
fn test_underflow() {
    let config = MemoryManagerConfig::try_new_limit(100, 0.5).unwrap();
    let manager = MemoryManager::new(config);
    manager.grow_tracker_usage(100);

    manager.register_requester(&MemoryConsumerId::new(1));
    assert!(!manager.can_grow_directly(20, 0));
}

Expected behavior

Additional context