Change benchmark unit of time from nanoseconds to seconds

[qxzzxq]

Is your feature request related to a problem? Please describe.
The actual benchmark message use nanosecond as the unit of time, which doesn't fit our use case as ETL workflow often lasts much longer.

Describe the solution you'd like
In com.jcdecaux.setl.internal.BenchmarkInvocationHandler, use seconds to measure the elapsed time.