Debugger::timer: switch from microtime to hrtime

hrtime is faster on virtual machines, due microtime use system call that need to change context from user to kernel (PHP7.3+)

src/Tracy/Debugger/Debugger.php

@@ -503,10 +503,10 @@ public static function dump(mixed $var, bool $return = false): mixed
 	public static function timer(?string $name = null): float
 	{
 		static $time = [];
-		$now = microtime(true);
+		$now = hrtime(true);
 		$delta = isset($time[$name]) ? $now - $time[$name] : 0;
 		$time[$name] = $now;
-		return $delta;
+		return $delta / 1e+9;
 	}