Enhance UWSGI configuration and observability

[benoit74]

Issues like #882 are showing that we have difficulties with the UWSGI management.

We should:

• better understand what are the proper UWSGI settings and have some rule of thumb to configure them
• decide which UWSGI base image we should use (currently we use an image with nginx but the we are still not sure this is the good choice)
• better understand how to monitor UWSGI server and other components around like the TCP stack (number of processes, workers, memory, queues, ...)

Note that we should probably tackle #832 at the same time