New reader to read journald using jounralclt. The reader can read from
files and supports matchers.

A test is added to compare both readers.

Commit new reader and add timestamp parsing

Improve comparison test by removing fields that were not present in
the go-systemd implementation.

Add a journal file to test matchers and some example code of how to
generate a user journal file for testing

This commit fully removes the `jouranlread` package that was
responsible for reading the journal using
`github.com/coreos/go-systemd/v22/sdjournal`.

The seek mode is also greatly simplified.

Because we're tailing journalctl, having a backoff config does not
make sense any more.

- Remove unused methods
- Remove unused variables
- Fix error wrapping formatting
- Simplify code

- Fix types
- Remove unused code/config options
- Refactor variable names
- Fix typos and documentation
- Clean up log entries
- Improve error messages

Add documentation to all exported methods and types from
`journalctl/reader.go`.

`Reader.Next` now returns immediately if the cancel is cancelled.

- Gracefully terminate input on canceller cancellation, the Reader now
returns ErrCancelled then the journald input reads it and gracefully
returns without bubbling up the error

- Journal events are now parsed as map[string]any because in some
cases there can be binary data like in some core dumps.

This commit fixes two problems:
- The output from stderr was read and sent to a channel, but the
channel was never read.
- Stderr was read in memory until EOF, which could lead to an
uncontrolled memory growth.

Now each line is sent to an unbuffered channel until EOF or an read
error occurs. The Stop method now reads from this channel until the
end (channel close) or a timeout of 1 minute occurs.

The locale/timezone from the host running the the test could generate
a timestamp object different from the golden events, this commit fixes
it by comparing them with their `Equal`.

On TestInputSeek set the since option to a time between the first and
second entries to avoid issues with different hosts.

The since tests was broken because newer versions of Jouranlctl
accepts time stamps on RFC3339, but older versions do not.

The Reader now formats the since parameter in a format accepted by
older versions of systemd. The since tests ensures the timestamp is in
the local timezone to avoid conflicts with jouranlct.

This commit fixes tests that were failing due to an incompatible
journal version. The new journal file was generated with journald
249 (249.11-0ubuntu3.12).

This commit adds the missing syscalls to our seccomp policy so
Filebeat can start the journalctl process.

The syscalls were acquired by running Filebeat with the seccomp
default action set to "log", and running Auditbeat to collect those
logs and convert the syscall number into a name accepted by our
seccomp policy.

Add the correct syscalls to the changelog and move the entry under
breaking changes.

…eats into journalctl-for-journald-input

Fix merge conflicts in the changelog and improve working of one entry.

Re-add a syscall that was mistakenly removes from the default seccomp
policy.

Fixes a log entry that was mixing keys with data