HSEARCH-1739 Rename SearchFactoryBuilder to SearchIntegratorBuilder
HSEARCH-1740 Prefer using SearchIntegrator over SearchFactoryImplementor wherever possible
HSEARCH-1740 Move SearchFactoryImplementor to a dedicated 'impl' package
HSEARCH-1730 Move all .impl classes in hibernate-search-engine into engine.impl
HSEARCH-1673 Move SearchMappingBuilder to be an SPI
HSEARCH-1673 InfinispanDirectoryProvider also promoted to SPI
HSEARCH-1673 Promote DirectoryBasedIndexManager to an SPI package
HSEARCH-1673 Expose the default SimpleInitializer reference to SPI without exposing the implementation class