Goal:

Stops having to ssh to a bot to get the logs for a task. Instead, the process specific logs (task_runner.py, run_isolated.py) for a task are stored along the task inside TaskOutput<id=foo.log>.


AIs:

Bot:
- bot_main: after reaping a task, creates a task specific log directory "logs/<task_id>/" and instruct task_runner (and incidentally run_isolated) to use it instead of "logs/".
- bot_main: upon task_runner termination, bot_main "amends" a task with the task logs. 

Server:
- Update task/ endpoint group to retrieve named resources. This is also needed for stdout/stderr disambiguation as per issue 732802.


Alternative:

- Store on the isolate server. It has the advantage of automatic cleanup but enforce close coupling with isolate server, which I prefer not to.


Adapted from https://github.com/luci/luci-py/issues/291