Include date and time zone in log message timestamp

Modify the log4j2.xml so the pattern includes the date.

For easy cross-referencing with logs from other Couchbase services, use ISO 8091 format with time zone offset specified as HH:MM.

For example:

2022-10-03T15:46:35,496-07:00 

It would be idea if we could use a period instead of a comma to indicate fractional seconds (like other Couchbase logs), but log4j2 doesn't have an easy way to do that when including the offset, and it doesn't seem like a huge deal.