Arun Kannawadi discovered on DM-24737 that Config.validate isn't being called on measurement plugin configs, even though it should be. I'm not sure if this is because RegistryField or ConfigurableField isn't calling validate on its child configs, or if we've just forgotten to call super().validate() somewhere in a validate implementation.

We should probably consider modifying pex_config to make that super delegation unnecessary - if we do that first, and we still have some validate implementations that do delegate to super, we'll validate twice, but that's not a big deal, and we can clean it up slowly.