Merge pull request #15472 from keszybz/dbus-api-docs

A few more dbus api documentation updates

diff --cc NEWS
Simple merge

diff --cc TODO
Simple merge

diff --cc man/systemd-nspawn.xml
Simple merge

diff --cc man/systemd.network.xml
Simple merge

diff --cc src/hostname/hostnamed.c
Simple merge

diff --cc src/libsystemd-network/sd-dhcp-lease.c
Simple merge

diff --cc src/resolve/resolved-bus.c
Simple merge