StandardQueryConfigHandler shoud overwrite toString() to show its configs [LUCENE-4328]

StandardQueryConfigHandler shoud overwrite toString() to show its configs. Now,System.out.println("handler: " + queryParser.getQueryConfigHandler().toString());
only get "handler: org.apache.lucene.queryparser.flexible.standard.config.StandardQueryConfigHandler@3bc257"

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Migrated from [LUCENE-4328](https://issues.apache.org/jira/browse/LUCENE-4328) by wunan23

Start by locating StandardQueryConfigHandler in the queryparser flexible standard configuration code and inspect how its configuration state is represented. Verify the current output shown in the issue, then make the handler's string representation show its configs and confirm that printing it no longer produces only the default class-and-hash form.

Written by the indexing model from the issue text.