Add BC performance knowledge from OptimAL learnings

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

microsoft/knowledge/performance/prefer-modifyall-over-per-row-modify.good.al

@@ -20,6 +20,7 @@ codeunit 50242 "Perf Sample ModifyAll Good"
         StagingEntry: Record "Perf Import Staging Entry";
     begin
         StagingEntry.SetRange("Batch ID", BatchId);
+        StagingEntry.SetRange(Processed, false);
         // Processed has no OnValidate logic, and the equivalent loop uses Modify(false).
         StagingEntry.ModifyAll(Processed, true, false);
     end;