Make sure package names don't contain invalid/unprintable chars

[christophebedard]

This aims to detect my mistake here: ros2/rclpy#1629 (comment). I copied a package name from the GitHub PR files list, which included an invisible Unicode character (U+200E LEFT-TO-RIGHT MARK, UTF-8: E2 80 8E). This was very hard to figure out just by looking at the weird CI failure:

Package '‎rclpy' specified with --packages-above-and-dependencies was not found

With this PR:

$ ros-ci-for-pr -p ros2/rclpy#1629 -k ‎rclpy -t rolling -b -c
usage: ros-ci-for-pr [--branch BRANCH] [-p PULLS [PULLS ...] | -i] [-h] [-k PACKAGES [PACKAGES ...]] [-t TARGET] [-b] [-c] [--only-fixes-test] [--colcon-build-args COLCON_BUILD_ARGS]
                     [--colcon-test-args COLCON_TEST_ARGS] [--cmake-args CMAKE_ARGS]
ros-ci-for-pr: error: argument -k/--packages: package name contains unprintable characters: '\u200erclpy'

[MichaelOrlov]

LGTM