Feature: add executor.create_future() (backport #1495)

[mergify]

Part of #1399 and #1469.
To allow an executor to reschedule a task when a future stops blocking, it is crucial that the future is attached to the same executor.
Currently, users are able to initialize a Future instance without supplying the executor parameter.
This behavior is necessary to allow calling client.call_async() before attaching the node to an executor (the future is attached to the running executor when processing the service response).

In asyncio, loop.create_future() was added to discourage users from initializing the Future class directly.
I suggest we follow the same path.

---

This is an automatic backport of pull request #1495 done by Mergify.

[mergify]

Cherry-pick of bcdd663 has failed:

On branch mergify/bp/jazzy/pr-1495
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Changes to be committed:
	modified:   rclpy/rclpy/executors.py

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   rclpy/src/rclpy/events_executor/events_executor.cpp
	both modified:   rclpy/src/rclpy/events_executor/events_executor.hpp
	both modified:   rclpy/test/test_executor.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[fujitatomoya]

@nadavelkabets can you review this? i did fix several conflicts.

[fujitatomoya]

Pulls: #1500
Gist: https://gist.githubusercontent.com/fujitatomoya/cd36c4c5f66a91d06ba8f7f6031f5077/raw/eb309f25e7920229a1794054e9234523cf447b6e/ros2.repos
BUILD args: --packages-above-and-dependencies rclpy
TEST args: --packages-above rclpy
ROS Distro: jazzy
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/16962

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