Filing this as a separate ticket to keep the immediate fix for AF-17643 more minimal so it can be backported easily if needed.

From lynne.wang@mongodb.com's comment in AF-17643:

• Outside of the feature flag checks in the expCtx, there are ~28 other sites in the codebase that derive the VersionContext straight from an expCtx's opCtx (from a quick sweep with Claude). These are most likely paths that expect to run with a live opCtx, but it may be worth verifying whether these could be reached from one of the paths mentioned above and may also benefit from the null opCtx fallback. This could be done as a follow-up ticket after addressing the feature flags in the ExpressionContext first.