It is very annoying that I/O timed out tasks do not have any performance statistics saved, because run_isolated doesn't return fast enough with the 1 minute SIGTERM. This made diagnosing  issue 794085  much harder than necessary.

AIs:
- Make task_runner give more slack to run_isolated to initiate its own termination procedure. Uploading files back may take more than grace period, basically the termination duration shouldn't be tied to grace_period at all.
- Make run_isolated save inputs stats as it is happening, at a reasonable rate (?)