Support for finer timestamp resolution

[tkowalcz]

Currently Tjahzi timestamps all logs using milliseconds precision timer. It is provided by log4j via getTimeMillis method on LogEvent.

Log4j and Loki supports finer precision timestamps. On Log4j side these are available via getInstant method. We should use that instead of getTimeMillis.

Discussed in #95

^{Originally posted by thgau August 26, 2022}
I use the Thahzi with log4j and I see that the loki timestamp always has 000000 in the micro/nanoseconds part.
log4j is able to give the timestamps with finer resolution. I can put these into the text part. But still it does not reach the loki timestamp.