host build: optimistic_yield() wrongly delays() instead of avoiding e…

…xcessive yields (#6802)

* optimistic_yield is a yield, not a delay, and avoids yielding if last yield has occurred recently enough.

* Suppress an unused argument warning.

Co-authored-by: Earle F. Philhower, III <earlephilhower@yahoo.com>

tests/host/common/Arduino.cpp

@@ -44,7 +44,7 @@ extern "C" bool can_yield()
 
 extern "C" void optimistic_yield (uint32_t interval_us)
 {
-    usleep(interval_us);
+    (void)interval_us;
 }
 
 extern "C" void esp_yield()