Add the ability to configure agent logging

[mach6]

Adds the ability to specify the logging driver and
options for the runner (agent), gc, and watchtower
containers.

Example config;

DRONE_AGENT_LOGGING_DRIVER=json-file
DRONE_AGENT_LOGGING_OPTIONS=max-size:100m,max-file:5

ref: https://docs.docker.com/config/containers/logging/configure/#supported-logging-drivers

[mach6]

@bradrydzewski @tboerger Any feedback on this one? Cheers.

[tboerger]

Why don't you just define the logging driver on Docker daemon level? IMHO it doesn't make sense to define that per container.

[mach6]

Why don't you just define the logging driver on Docker daemon level? IMHO it doesn't make sense to define that per container.

While one can certainly do this; the intent with the per container config options is to enable finer configuration. for example; If one does not want the drone-gc or watchtower logging behavior to be the same as the agent. Maybe one wants the agent logs to leverage the gcplogs driver and drone-gc to leverage json-file, for example.

Also, setting the behavior at the daemon level impacts the logging behavior of the containers which support pipeline steps.

[mach6]

@tboerger @bradrydzewski any additional thoughts on this one?

[mach6]

PR re-based against v1.8.1 and force-pushed