Allow rclcpp::Time::max() to support other clock types than RCL_SYSTEM_TIME.

[jrutgeer]

As of yet, rclcpp::Time::max() calls the Time() constructor without specified value for rcl_clock_type_t:

rclcpp/rclcpp/src/rclcpp/time.cpp

Lines 278 to 282 in fff009a

	Time
	Time::max()
	{
	return Time(std::numeric_limits<int32_t>::max(), 999999999);
	}

Hence, rclcpp::Time::max() returns a Time value with clock type RCL_SYSTEM_TIME:

rclcpp/rclcpp/include/rclcpp/time.hpp

Line 46 in fff009a

Time(int32_t seconds, uint32_t nanoseconds, rcl_clock_type_t clock_type = RCL_SYSTEM_TIME);

This means that you can't compare time values of type RCL_ROS_TIME to rclcpp::Time::max().

I propose to change the max() implementation as follows:

Time
Time::max(rcl_clock_type_t clock_type = RCL_SYSTEM_TIME)
{
  return Time(std::numeric_limits<int32_t>::max(), 999999999, clock_type);
}

This is backwards-compatible with the current implementation, yet allows to specify RCL_ROS_TIME if needed, e.g.:

if( reported_time_ < rclcpp::Time::max(RCL_ROS_TIME) {
  [...]
}

[fujitatomoya]

@jrutgeer it would be appreciated if you review #2348

[fujitatomoya]

@jrutgeer this has been addressed by #2352, i will go ahead to close this. (i gave up backporting this to iron and humble, since this requires ABI change. see #2355 (comment))