Miscellaneous Cleanups For The FM Subsystem

I'm using this as a bit of a staging ground for things that are, IMO, pretty easy clean-up changes, but invasive enough that I don't want to do them as a part of other FM-related changes.

• https://github.com/oxidecomputer/omicron/pull/10592/changes#r3606250554 - use a macro for "expecting columns" from kinded fact types.
• https://github.com/oxidecomputer/omicron/pull/10592/changes#r3606101391 - Split out fact-types in a per-DE module
• https://github.com/oxidecomputer/omicron/pull/10866 + https://github.com/oxidecomputer/omicron/pull/10592/changes#r3606255152 - Change SagaSummary to use the Selectable/Queryable model.
• https://github.com/oxidecomputer/omicron/pull/10592/changes#r3606347834 - it would be nice to either proptest or exhaustively iterate over "all DEs, all facts" and see that foreign facts get treated consistently (the case gets closed)
• https://github.com/oxidecomputer/omicron/pull/10541#discussion_r3415749951 - Derive macros for DB models / sitrep types to ensure they have the necessary ID types to be contained within a sitrep (and GC'd from a sitrep that gets deleted too)
• https://github.com/oxidecomputer/omicron/pull/10592/changes#r3606457099 - Parallelize planning input loading

Review the linked discussions in PRs 10592, 10866, and 10541 to choose one of the six cleanup items in the FM subsystem. Trace the relevant fact types, SagaSummary, DB models, or planning input loading from those references; the selected checklist item is done when its stated cleanup and associated consistency or model requirements are satisfied.