Support for adding custom ruleset queries to SAST IaC

Proposal

Born out of a question on &6653 (comment 772404427) we should look into the effort to support injection of custom queries into our IaC analyzers, notably kics.

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We don't yet support custom queries for kics, unfortunately. I think this should be possible in the future by improving our custom ruleset configuration to support specifying kics --queries-path setting but it's not yet available.

We also need to test further around this approach since kics currently assumes the presence of a corresponding metadata.json definition alongsid the rego config. It seems unreasonable to expect users to provide that as well so we will need to figure out some magic around generating metadata alongside the queries and will have to look into this further. Opened #348371 to do so.