import: rename 'poll-dck' to 'pull-dkr'

I figure "pull-dck" is not a good name, given that one could certainly
read the verb in a way that might be funny for 16year-olds. ;-)

Also, don't hardcode the index URL to use, make it runtime and configure
time configurable instead.
run: add a new "-t" mode for invoking a binary on an allocated TTY
machinectl,nspawn: don't print extra final newline if pty terminal output was newline-terinated anyway
systemd-run: add --quiet mode to suppress informational message on TTY usage
machined: add OpenMachinePTY() bus call for allocating a PTY device within a container

Then, port "machinectl" over to make use of it.
systemd-run: support -t mode when combined with -M

For that, ask machined for a container PTY and use that.
nspawn,pty: port over to new ptsname_malloc() helper
util: add allocation loop to gettyname_malloc()
update TODO