Include QString

[mjforan]

Adds #include <QString> to all files which use QString.

Addresses @clalancette's comment here. The linter's "include what you use" rule does not work on this header. Probably other QT headers as well, but this is the most common.

[ahcorde]

Pulls: #1298
Gist: https://gist.githubusercontent.com/ahcorde/1453a997533c1caec0186b8c578031a6/raw/88b5b66f9df531bcbe781bc48d285e773327c393/ros2.repos
BUILD args: --packages-above-and-dependencies rviz_common rviz_default_plugins rviz_visual_testing_framework rviz_rendering --packages-above-and-dependencies rviz_common rviz_default_plugins rviz_visual_testing_framework rviz_rendering
TEST args: --packages-above rviz_common rviz_default_plugins rviz_visual_testing_framework rviz_rendering --packages-above rviz_common rviz_default_plugins rviz_visual_testing_framework rviz_rendering
ROS Distro: rolling
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/14812

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