journal: don't go belly up when an stdout/stderr client terminates the connection
journald: cache hostname, boot_id and machine_id fields instead of generating them fresh for each log entry
journal: when listing logs of a container make sure we don't accidentally show messages from host too
journald: cache cgroup root path, instead of querying it on every incoming log message
units: don't run readahead done timers in containers

We don't run the collector in the container either, hence we don't need
to stop it either.
journald: make sure the stdout/stderr stream fd is removed from epoll before we close it
sd-event: try to move each wakeup to the same spot within every 10s

In addition to the same spot within every 1min, every 1s, every 250s
bus: connect directly via kdbus in sd_bus_open_system_container()

kdbus fortunately exposes the container's busses in the host fs, hence
we can access it directly instead of doing the namespacing dance.
bus: when checking whether a creds object contains some field, don't use assert_return()

These are not programming errors, so they shouldn't use assert_return()
bus: update name listing logic to current kernel interface
update TODO
bus: fix order in which we check creds
bus: properly generate NameOwnerChanged messages when we take from/give back to queue/starter
test-fileio: replace mktemp with mkstemp to avoid warnings

This is a fairly useless thing to do but it makes the compilers
and analyzers shut up about the use of mktemp.
timedated: make sure GetAll() succeeds in systems lacking /dev/rtc (such as containers)
service: actually leave watchdog enabled in the states where it matters
man: mention SYSTEMD_USER_WANTS

Also split into paragraphs for easier reading and make a few minor
corrections.
journal: pipe journalctl help output into a pager

journalctl help output might run off the screen, so be consistent
as other systemd tools do and pipe it into a pager.
Do not log all assert_return failures

% build/journalctl help
Assertion 'match_is_valid(data, size)' failed at ../src/journal/sd-journal.c:227, function sd_journal_add_match(). Ignoring.

Callers cannot be expect to check all arguments always.
nspawn: complain and continue if machine has same id

If --link-journal=host or --link-journal=guest is used, this totally
cannot work and we exit with an error. If however --link-journal=auto
or --link-journal=no is used, just display a warning.

Having the same machine id can happen if booting from the same
filesystem as the host. Since other things mostly function correctly,
let's allow that.

https://bugs.freedesktop.org/show_bug.cgi?id=68369