- add support for PostgreSQL version 17, we now use dedicated
  function pg_walfile_name_offset to retrieve filename and
  check if offset is 0.
- database_local: set checkpoint timeout lower.
- add support for nanosecond integer resolution.
  + use ns in self.last_backup_stop_time as datetime object
    are not serializable.
  + use ns for start_backup_time and remove datetime usage
    for file comparison.
  + this support allow the plugin to not backup each time the
    latest wal file.
- add fix for pg8000 < 1.30 returning a string instead tuple
  with pg_walfile_name_offset.
- add a check if ROP last_time_backup is large enough
  or convert it to ns (ease plugin version migration).
- remove unused modules datetime dateutil.
- use constant for `NANOSECONDS_PER_SECOND` and
  `LAST_BACKUP_TIME_WITH_SECONDS`
- limit if/else block by using global functions current_time_ns()
- add comment about time.time_ns() when to remove it (python 3.7 eol)
- use directly os.stat().st_mtime_ns it has been introduced in
  python 3.3 and we don't support python <= 3.6.
- add comment about checkpoint_timeout parameter in setup-local-db.
- use stat_obj instead of stat to avoid keyword redefining.
- improve docstring for __decode_lsn_filename_offset which return
  True.
- remove unused lsn parameter from __wait_for_wal_archiving.
- add debug message when LAST_BACKUP_TIME_WITH_SECONDS is hit.

Signed-off-by: Bruno Friedmann <bruno.friedmann@bareos.com>
Co-authored-by: Sebastian Sura <124262655+sebsura@users.noreply.github.com>

Introduce newly accepted adr for python code:
0003-always-use-integer-when-comparing-timestamp-numbers-in-python

Fix typo in README.md

Signed-off-by: Bruno Friedmann <bruno.friedmann@bareos.com>
Co-authored-by: Sebastian Sura <124262655+sebsura@users.noreply.github.com>