Modified clock design, added new time source

[patrykantosz]

What does this PR do?

Changes the current design of the Clock source and adds new time source - the ROS 2 frame. Now there is only one Clock, ROS2Clock, which can be configured to work with different time sources. The Clock can also publish time to the /clock topic - this option is enabled by default. There are three TimeSources:

• realtime - it starts on the start of the simulation (or on the start of the application, when you use Editor). Can be affected by the jitter in the data, simulation computations or other similar events.
• simulation - provides timestamps calculated using updates from the physics engine. Simulation paces the clock with stable steps, and as a result, this time source eliminates data jitter. This is a default time source.
• ros2 - provides the time taken from the ROS 2. By default this is system_time but it can be configured to provide the time from the other sources.

Clock can be configured via .setreg file or by passing --setreg flags in the command line. Example: ./build/linux_working/bin/profile/Editor --regset="/O3DE/ROS2/ClockType=ros2" --regset="/O3DE/ROS2/PublishClock=true"

How was this PR tested?

By checking if ROS 2 /clock topic is available and checking timestamps there for each of the time sources.

[amzn-changml]

This has passed AR, but the status is stuck on an older review: https://jenkins.build.o3de.org/blue/organizations/jenkins/o3de-extras/detail/PR-707/5/pipeline. Moving to override now.

[o3de-issues-bot]

Initial AR build failed https://jenkins.build.o3de.org/job/o3de-extras/job/PR-707/3/display/redirect. Status check rule override by amzn-changml