Retire the Fallback Scheduler

[nhoening]

The fallback scheduler (which most often produes zeroes) is used for `InfeasibleProblemException´. We implemented it for a reason, but I'm not sure how often it does anything useful. On the bad side, the fallback scheduler hides which failure happened, which makes inspecting scheduling.

Later, we implemented relaxing SoC constraints, which makes the fallback less needed. Specifically, we

• turn on the (SoC) relaxations by default.
• remove the fallback scheduler
• check if documentation should change according to the two points above