Move pipeline templates to gitlab-ci subdirectory

This change makes it possable to use these templates directoty as
templates in gitlab by nominating the repo as a template repo as defined
here: https://gitlab.oss.arm.com/help/user/admin_area/settings/instance_template_repository.md#supported-file-types-and-locations



Signed-off-by: Drew Reed <Drew.Reed@arm.com>