Time-based JCA metrics do not specify measurement unit

JCA metric attributes are created dynamically based on IronJacamar org.jboss.jca.core.spi.statistics.StatisticsPlugin.
It is not possible in the JCA subsystem to determine if the statistic is a time-based metric and how it is measured.

This would require an update to StatisticsPlugin to support some kind of measurement unit.

Identifed metrics:

• Datasources
• average_blocking_time {data_source="ExampleDS",}
  * average_creation_time{data_source="ExampleDS",}
• average_get_time {data_source="ExampleDS",}
  * max_creation_time{data_source="ExampleDS",}
• max_pool_time {data_source="ExampleDS",}
  * total_blocking_time{data_source="ExampleDS",}
• total_creation_time {data_source="ExampleDS",}
  * total_get_time{data_source="ExampleDS",}
• max_wait_time {data_source="ExampleDS",}
  * total_creation_time{data_source="ExampleDS",}
• average_pool_time {data_source="ExampleDS",}
  * average_usage_time{data_source="ExampleDS",}
• max_usage_time {data_source="ExampleDS",}
  * total_pool_time{data_source="ExampleDS",}
• total_usage_time {data_source="ExampleDS",}
  * xacommit_average_time{data_source="ExampleDS",}
• xacommit_max_time {data_source="ExampleDS",}
  * xacommit_total_time{data_source="ExampleDS",}
• xaend_average_time {data_source="ExampleDS",}
  * xaend_max_time{data_source="ExampleDS",}
• xaend_total_time {data_source="ExampleDS",}
  * xaforget_average_time{data_source="ExampleDS",}
• xaforget_max_time {data_source="ExampleDS",}
  * xaforget_total_time{data_source="ExampleDS",}
• xaprepare_average_time {data_source="ExampleDS",}
  * xaprepare_max_time{data_source="ExampleDS",}
• xaprepare_total_time {data_source="ExampleDS",}
  * xarecover_average_time{data_source="ExampleDS",}
• xarecover_max_time {data_source="ExampleDS",}
  * xarecover_total_time{data_source="ExampleDS",}
• xarollback_average_time {data_source="ExampleDS",}
  * xarollback_max_time{data_source="ExampleDS",}
• xarollback_total_time {data_source="ExampleDS",}
  * xastart_average_time{data_source="ExampleDS",}
• xastart_max_time {data_source="ExampleDS",}
  * xastart_total_time{data_source="ExampleDS",}