Feature request

Related with ros2/ros2#649. The idea is to measure the performance of rclcpp communication, so in the future we can compare different intraprocess mechanisms, intraprocess vs interprocess, etc.

Feature description

Check here: https://gist.github.com/ivanpauno/daee6069a034dabb6374c0d987162cf6

Implementation considerations

Planned tasks:

1. Use cpp timers to measure publish-to-subscription latency and publish/subscription rate. Log results (Added rclcpp_performance package #636).
2. Use gperftools to measure cpu/memory usage, publish/subscribe operation time.
3. Parameterize the test, for varying message length, publishing/subscribers, publishing rate.