Split optional and required kernel configs into separate files.
readme: describe how our kernel configs are generated from Buildroot
readme: document QEMU `-no-reboot` and speculate gem5 `panic_on_panic`
in preparation for some more automated bisection with ktest.
Otherwise it was getting messy to distinguish between trace-events
and trace-<pid> in the .gitignore.
Now only the latest trace will be kept, with a fixed name.
We have wanted to do this since forever, but the last straw was gem5 aarch64,
which runs too fast, and makes it very hard to write "root" withing 60 seconds!
Another possibility to solve that would have been to find an answer for:
https://unix.stackexchange.com/questions/340333/how-can-i-get-bin-login-to-not-timeout
which we didn't, but not typing root at all is even better.
Take this opportunity to document how to login into user0.
sshd: automate and document further
gdbserver: automatically startup internet on /gdbserver.sh
