Currently, we exempt any aggregation that has a writing stage in it. In practice, there may be large amount of blocking block before we get to that write, so it could be safe to shed in some cases.

Implementation note from SERVER-135600 review: LoadSheddingOpState::_eligible is currently one-way (markEligible() only), and its relaxed atomic access relies on that. The queued-operation sweep reads it from the monitor thread, then calls killOperation later, so making eligibility revocable ("eligible until the write phase") opens a check-then-kill race that stronger memory ordering won't fix. Prefer building on the existing latched wasGlobalLockTakenForWrite() guard in isShedCandidate(), which relies on the interrupt check when the IX lock is taken. If a revocable flag is truly needed, clear it and then check for interrupt before the first write, and revisit the relaxed-ordering comment.