Reformat overlong table into a list-table to make it easier to edit.
The change contains no wording changes besides giving titles to the
list-tables.
Fix formatting for setup-devstack-source-dirs so that the variable does
not get displayed with a grey bar at
https://docs.openstack.org/devstack/latest/zuul_roles.html#role-setup-devstack-source-dirs
Change-Id: I7378d46c507b1d86f1d5319655a55f2a8c5a8f60