Add unixy support for check_mode_markers (#7179)
* Add unixy support for check_mode_markers
Modifies output on playbook start, task start, and handler start when
playbook runs in check mode.
* changelog fragment
* Address feedback
* Oops
(cherry picked from commit 631d215fe8)
Co-authored-by: akatch <akatch@users.noreply.github.com>