DocumentExtractor to use the new FieldLoadingVisitor strategy: old method was removed
IndexReader instances are now opened via DirectoryReader
Analyzers: apply required changes to use the Analyzer framework and adapt to new Solr classloading
Fix tests: CompressionTest
Document.getFieldable is now getField (and returns a different type)

Also, Field no longer implements Fieldable
Searcher instances no longer require to be closed (and close() method was removed)

Needless to say, you still need to close the IndexReader which was provided to the Searchers.
[SPI] We changed the createTimeoutException() API
Fix StoreNormsTest: Field#getOmitNorms method is gone
Fix test WorkDoneOnEntitiesTest
More IndexReader open replaced
Fix test: SharingBufferIndexProviderTest
[API] SortField type is now an inner enum SortField.Type.STRING
Reintroduce as deprecated the addNumericFieldToDocument helper, fix NumericField tests
Reuse our EMPTY_DOCIDSET implementation in tests
Update DocIdSet tests and add one for the Elias-Fano encoder
Fix test: SortTest
Filter implementation updates
[!WARNING!] Reimplement the search engine
Update tests: ProvidedIdTest
Fix test: NumericBigDecimalBridgeTest