Refactor: base clock

[nadavelkabets]

Part of #1620

Changes

• New BaseClock class
• Clock class retains the blocking sleep_for() and sleep_until() methods
• Following rclcpp, ROSClock deprecated in favor of Clock(clock_type=ClockType.ROS_TIME)`
• JumpHandle, TimeSource and ThrottleContext now accept BaseClock
• TimeSource checks ClockType instead of isinstance()
• ROSClock is kept as thin deprecated subclass for backwards compatibility

Notes

• Users with SYSTEM_TIME and STEADY_TIME can now call ros_time_is_active() and set_ros_time_override(). Similar to rclcpp, RCLError is raised if the clock is not a ROS_TIME clock
• Removed Clock.__new__ - surprising behavior that silently returned a ROSClock instance when Clock was initialized with clock_type=ROS_TIME

[mjcarroll]

@nadavelkabets just a note (from @InvincibleRMC) that resolute (26.04) is going to be using Python 3.14, which does introduce some AsyncIO API changes.

You may want to pre-test what you have here for when we make the jump later this month.

[mjcarroll]

Approve with a single nit and green CI.

Overall a solid refactor.

[mjcarroll]

I'll run CI after you address the nits. Should be fine.

• Linux
• Linux-aarch64
• Linux-rhel
• Windows

[nadavelkabets]

@nadavelkabets just a note (from @InvincibleRMC) that resolute (26.04) is going to be using Python 3.14, which does introduce some AsyncIO API changes.

You may want to pre-test what you have here for when we make the jump later this month.

I checked the 3.13 and 3.14 changelogs - 3.13 adds keyword argument passing to the task constructor and some new util functions, and 3.14 adds task introspection. Neither affects us.
I agree it's valuable to pre-test against 3.14. Will do that for the AsyncNode feature.