Remove dubious jmx / metrics categories

When I look at Solr's metrics or browse the JMX tree or even in Solr's admin UI in certain areas, I see that many parts of the original & fast vector highlighter are present here under the category HIGHLIGHTER. I don't think they should be; they don't warrant it. Who cares how many times HIGHLIGHTER.SolrFormatter.default.requests has been used? One could argue any number of these and just about any class in the whole system might be interesting to know in some perf investigation so why are these so special. They aren't. For that matter, nor is SPELLCHECK and some others.

It might be interesting for SearchHandler to report metrics on the components that are there and how often they are used. That would be cool. But down to the detail of which internal components are used within a SearchComponent is a bit much.

CC ab