more logging improvements
snapshot staging tasks

We don't load them yet, but it's useful for metrics and tests.
unregister task when buildpack cache upload fails

Previously the error would be swallowed and the task would never respond
or be unregistered. This would cause it to consume resources until the
DEA was bounced.

[finishes #58671838]
Check the temp folder size it test
bump timeout for killing DEA

1 second is not enough for it to reliably stop all instances/staging
tasks.