This should allow us to avoid a lot of useless processing when iterating over the
whole main database (unlink/remap/usages checks/etc.).
Note that some ID types report they can use any type for now, due to
fuzzyness/indefined nature of some usages (like constraints/modifiers/game logic,
or ID pointer of nodes...). Maybe we could address this (like e.g. adding defines
in relevant headers to restrict ID types used by constraints, by modifiers, etc.).
But don’t think this is top priority for now.
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