Fix elements staying streamed in after leaving an activated sector

[Flashmyname]

Summary

OnElementEnterSector adds an element to the active list when it enters an activated sector, but nothing removes it when the element moves out of one into a sector that is not activated. It is queued for stream out and still left in m_ActiveElements and m_ActiveElementSet, so Restream pulls it back in on the next pulse.

It is now removed there, the same way RemoveElement does it (CClientStreamer.cpp:332-333).

Motivation

The element stays streamed in even though its sector is not active, and it stays in the list that DoPulse walks and sorts every frame for the rest of the session.

Test plan

Objects use 300 unit sectors, a 3x3 activated block and a 500 unit stream distance, so the window only exists when the player stands near a sector edge. With the player at x=2095 the block ends at 2400: 60 objects created next to the player, then moved to x=2495, which is outside the block and 400 units away.

before   streamed in after the move   60 / 60
after    streamed in after the move    0 / 60

Checklist

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