QTest::qWaitFor: move ceil<> to after the check

There's no reason to check whether the timer has expired after
rounding the timer's native nanoseconds up to milliseconds, so delay
the ceil<ms> operation to after the timer expiry check.

As a drive-by, protect the std::min call from Windows macros with the
parentheses trick and employ C++17 if-with-initializer.

Remove the break-if-expired, as it now obviously duplicates the while
exit condition.

Pick-to: 6.7
Change-Id: If30421012143640c75a9a44fe711d0c1c7cd23b9
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qtestsupport_core.h

@@ -43,11 +43,9 @@ qWaitFor(Functor predicate, QDeadlineTimer deadline = QDeadlineTimer(std::chrono
         if (predicate())
             return true;
 
-        const auto remaining = ceil<milliseconds>(deadline.remainingTimeAsDuration());
-        if (remaining == 0ms)
-            break;
+        if (const auto remaining = deadline.remainingTimeAsDuration(); remaining > 0ns)
+            qSleep((std::min)(10ms, ceil<milliseconds>(remaining)));
 
-        qSleep(std::min(10ms, remaining));
     } while (!deadline.hasExpired());
 
     return predicate(); // Last chance