Is your feature request related to a problem? Please describe.
Although the underlying com.google.logging.v2.LogEntry supports timestamps with nanosecond precision, com.google.cloud.logging.LogEntry only supports millisecond truncating the data.

Describe the solution you'd like
Replace the current long value representing milliseconds with com.google.cloud.Timestamp.

Describe alternatives you've considered
The only way is to use the protobuf classes directly or using ReST API which is cumbersome.

Additional context
N/A