Support triggering at multiples of a base rate

[callumforrester]

          With #65 this then becomes "Support OAV emitting frames at 1/N the rate of faster detectors"

Originally posted by @DiamondJoseph in https://github.com/DiamondLightSource/i22-bluesky/issues/63#issuecomment-2177996339

[DiamondJoseph]

So baserate is oav rate is f/N, detectors are triggered at f=N*baserate?

[callumforrester]

My understanding (@timsnow may correct me):

• The base rate is user-defined for the experiment in question and is the rate at which they want the fastest detectors (the tetramms) to go, 2500Hz might be a typical value.
• All detectors whose maximum speed is slower than the base rate (probably SAXS, WAXS and OAV) must go at the nearest multiple of the base rate they can to their maximum speed. The pilatuses can go up to 250Hz (so 10x slower in this case). The OAV can go at 23Hz, so in this case would go at 20Hz (125x slower).