WrappedDoubleValuesSource can leak IndexSearcher references

Cause of SOLR-13315

Index-specific DoubleValuesSources can be created by DoubleValuesSource.rewrite(), and the various consumers of these sources are careful not to store these rewritten sources on long-lived objects, such as queries that may be re-used between searchers.  However, the bridge code between ValueSource and DoubleValuesSource does not return a new object from its rewrite method, instead caching the passed-in IndexSearcher, which means references to this searcher may leak.