Make logging consistent

In postmarketOS, the logs are inconsistent; related for modem:

• NetworkManager -> syslog to memory (use logread command to read)
• ModemManager -> logging seems to be disabled by default?
• eg25-manager -> logging seems to be disabled by default?

others:

• tinydm logs to ~/.local/state/tinydm.log
• superd: ???

So let’s discuss, how can we make this more consistent?

• what would be good defaults?
• does logging to ram by default and only enabling persistent logging on demand still make sense to reduce flash wear?
• should we maybe use something else instead of busybox logging in postmarketos-base-ui? "logread" is quite limited

CC: @craftyguy