Freeing resources after device loss should use Device::trackers to find resources, not Device::life_tracker

[jimblandy]

At present, device loss uses LifetimeTracker::release_gpu_resources to find buffers to free. However, Device::life_tracker does not hold a complete record of all resources created with the device. For buffers, for example, it only mentions buffers that are waiting to be mapped or ready to be mapped. Device::trackers, however, holds a Tracker whose buffers field holds all buffers owned by the Device, which is exactly what device loss needs.

[jimblandy]

This would be a follow-up to #4851. CC @bradwerth

[teoxoy]

#5075 resolved this.