add support for bookworm syslog time format

add support for bookworm syslog time format

Adds `proxmox-time` as dependency to parse the timestamp

Since parse_rfc3339 can't handle microseconds, we try to remove the dot
followed by 6 digits of microseconds before passing it to parse_rfc3339.

A fallback to the previous format is used when when it fails to parse
the new format.

Signed-off-by: Mira Limbeck <m.limbeck@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>