Improve ISO building and testing throughput and latency

Originally created by @intrigeri on #11009 (Redmine)

As discussed on tails/tails#9264, tails/sysadmin#10996 and #10999 (closed), it would be good to:

• be able to run the test suite more frequently on our infrastructure
• improve the latency for ISO builds and tests

As elaborated on the blueprint, a first step would be to upgrade lizard v2 to give it more RAM, which will allow us to run more ISO testers and builders on it.

Blueprint: https://tails.boum.org/blueprint/hardware_for_automated_tests_take2/

Subtasks

• #10999 (closed)
• tails/tails#11010
• tails/sysadmin#11011
• tails/sysadmin#11113
• tails/sysadmin#11175

Related issues

• Related to tails/tails#9264