Cast Sequence to list on assignment

[InvincibleRMC]

Description

My proposal on what the solution for The Sequence Api discussion.
Zulip discussion here.

Is this user-facing behavior change?

Yes in the past users type would only change on receiving from a subscriber but, now the change is done on assignment to be more inline with numpy.array and array.array casts.

Did you use Generative AI?

Additional Information

[InvincibleRMC]

Pulls: #247
Gist: https://gist.githubusercontent.com/InvincibleRMC/f1a9a34556058d5f2a979c3525b1d7a4/raw/a2e37250150abb6a307758858c0fdf0a4d2dcecb/ros2.repos
BUILD args: --continue-on-error --packages-above-and-dependencies rosidl_generator_py
TEST args: --packages-above rosidl_generator_py
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18102

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

[InvincibleRMC]

Pulls: #247
Gist: https://gist.githubusercontent.com/InvincibleRMC/ee8648acbd36e3226191ea80afd32a7f/raw/a2e37250150abb6a307758858c0fdf0a4d2dcecb/ros2.repos
BUILD args: --continue-on-error --packages-above-and-dependencies rosidl_generator_py
TEST args: --packages-above rosidl_generator_py
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/18103

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

[InvincibleRMC]

For review I would recommend starting with #246 since its a clean refactor with no external changes. Whereas this builds upon to leverage the backend changes to avoid code duplication.