Merge pull request #15205 from jlebon/pr/preset-all-firstboot

manager: optionally, do a full preset on first boot

diff --cc man/systemctl.xml
Simple merge

diff --cc meson.build
Simple merge

diff --cc meson_options.txt
Simple merge

diff --cc src/core/manager.c
Simple merge

diff --cc src/systemctl/systemctl-show.c
Simple merge