machines.py: use columns with different widths

Set a fixed width for every column except the full_name column. This makes the column full_name to change width every time we resize the screen with a minimum of 10 characters. This allows for a lot of flexibility with the caveat that below 50 characters the dashboard isn't usable. Fixes: https://gitlab.freedesktop.org/mupuf/valve-infra/-/issues/82

machines.py: fix number of training boots Fixes: https://gitlab.freedesktop.org/mupuf/valve-infra/-/issues/83