Config validation should not enforce period configs exist for components which don't use it

[owen-d]

Namely, alter some of the logic introduced in #2564. Loki components, similar to our upstream project Cortex, should be able to run with the minimum set of configurations for the component in question. We should not be enforcing a non-zero number of Period Configs for components which don't rely on them.

[owen-d]

cc @sandeepsukhani @slim-bean

[stale]

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