Revert "Issue: painfully slow terrain loading. The cause is commit d9d995914c5fba00d4ccaf66b899384c8ea3d5eb (r/23185) -- the WaitOne on the UDPServer. Putting it back to how it was done solves the issue. But this may impact CPU usage, so I'm pushing it to test if it does."

This reverts commit 59b461ac0eaae1cc34bb82431106fdf0476037f3.
Try a different approach to slow terrain update by always cycling the loop immediately if any data was sent, rather than waiting.

What I believe is happening is that on initial terrain send, this is done one packet at a time.
With WaitOne, the outbound loop has enough time to loop and wait again after the first packet before the second, leading to a slower send.
This approach instead does not wait if a packet was just sent but instead loops again, which appears to lead to a quicker send without losing the cpu benefit of not continually looping when there is no outbound data.