Make throttle log macros accept a rclcpp::Duration

Feature request

Feature description

Currently RCLCPP_*_THROTTLE (and the RCUTILS_LOG_*_THROTTLE_NAMED which they cal) arbitrarily accept the duration as an integral value of milliseconds. This is highly confusing, especially since it is not documented anywhere but deep in the source, in RCUTILS_LOG_CONDITION_THROTTLE_BEFORE, where it calls:

static rcutils_duration_value_t __rcutils_logging_duration = RCUTILS_MS_TO_NS((rcutils_duration_value_t)duration); 

If it accepts a simple integral value, it at least should be in nanoseconds. Better yet, it would be nice to change the rclcpp side of the macro to accept an rclcpp::Duration, which would be very uniform, and then it can be converted to milliseconds to satisfy RCUTILS strange interface.

Implementation considerations

Being a macro, I'm not sure how to define this without breaking backward compatibility. However, that brings up the point: why do the rclcpp logging utils need to be macros? We could define a variadic function instead that wraps the RCUTILS C macros, right?

Start with the RCLCPP_THROTTLE macros and the RCUTILS_LOG_THROTTLE_NAMED macros, then inspect RCUTILS_LOG_CONDITION_THROTTLE_BEFORE where the duration is converted. Determine the backward-compatibility implications of accepting rclcpp::Duration and whether replacing the rclcpp macros with a variadic function is viable. Done means the API behavior and compatibility path are clearly established.