Migrate package dependency from vcstool to vcs2l.

[leander-dsouza]

Note

python3-vcs2l needs to be integrated with rosdep prior to the review of this PR.

Pull Request Description

Migrated ament_cmake_vendor_package dependency to use the maintained vcs2l package.

Future Work

This PR needs to be backported to the kilted and jazzy branches for consistency.

[cottsay]

We will need to carefully consider the rollout of this package because of the way vcs2l and vcstool are not co-installable. If someone has installations of multiple ROS distributions, we don't want this change to result in uninstallation of a previous distribution that depends on vcstool in order to upgrade to a new release of ament_cmake_vendor_package in a later distribution that uses vcs2l.

[leander-dsouza]

We will need to carefully consider the rollout of this package because of the way vcs2l and vcstool are not co-installable.

I guess then for now, we can focus on this being on rolling and lyrical so that it does not affect the currently active LTS distributions.