See merge request !1549

* Separate root and subscriber from drone SRs to avoid compilation of unnecessary dependencies
* display logs in debug mode

Rename subinstances to avoid conflict. Once a subinstance is allocated on a
computer, changing `sla-computer_guid` does not move the subinstance. Therefore
an instance name containing the computer's guid is necessary.

Fix logs printed out of the logging area

Process all available logs to avoid delay in log printing.

Indicate the time of the last received message in format hh:mm:ss .

Set c-astral SR in its own file and leave the autopilot used blank in software-base.cfg

Set publishing interval to 200 ms so radio network is not overflown

Allow subscribers' network interface to be different from the drones' one

* use the default RSA key length, instead of hardcoding 1024 (too weak) or 2048 (same as the current default).
* use SHA256 in certificates.

See merge request !1559

This reverts commit 3ff25131.

by default on riscv architecture, the libffi.so will be placed in
lib/lp64d but everywhere else in buildout (and especially for the
compilation of python3) we expect the lib to be in lib/ directory.

SlapOS.Eggs.UnitTest-Master.Python2 also installs old scipy so it needs
old gcc

See merge request nexedi/slapos!1557

Also remove old unused gcc version

unfortunately, there is no official release anymore so use a commit from
master.

This reverts commit 3d63cd39.

This reverts commit 1bd75eee.