Switch: how long support actually lasted

Ranked by the firmware history we hold, longest first. Every span is measured between the first and last firmware we saw, so each is a lower bound — no vendor here publishes a launch date, and support that began before the first release we know of is support we cannot count.

Only products whose support has demonstrably ended appear. A device still receiving firmware has a span that is still growing, and ranking it against finished ones would put the best-supported hardware at the bottom for still being supported.