totalTime metric should be milliseconds (not nano)

I observed that the "totalTime" metric has been a nanosecond number in recent years, yet once upon a time it was milliseconds. This change was very likely inadvertent. Our prometheus solr-exporter-config.xml shows that it thinks it's milliseconds. It's not; RequestHandlerBase increments this counter by "elapsed", the response of timer.stop() – nanoseconds. Years ago it had invoked MetricUtils.nsToMs but it appears ab removed this as a part of other changes in 2017 sometime – https://github.com/apache/solr/commit/d8df9f8c9963c2fc1718fd471316bf5d964125ba

Also, I question the value/purpose of this metric. Is it so useful that it deserves to be among our relatively few metrics exported in our default prometheus exporter config? It's been there since the initial config but I wonder why anyone wants it.