Use HStoreFile instead of StoreFile in our own code base and remove unnecessary methods in StoreFile interface

Cleanup the StoreFile interface. The metadata keys are moved to HStoreFile. These methods are removed: CacheConfig getCacheConf(); byte[] getMetadataValue(byte[] key); boolean isCompactedAway(); boolean isReferencedInReads(); void initReader() throws IOException; StoreFileScanner getPreadScanner(boolean cacheBlocks, long readPt, long scannerOrder, boolean canOptimizeForNonNullColumn); StoreFileScanner getStreamScanner(boolean canUseDropBehind, boolean cacheBlocks, boolean isCompaction, long readPt, long scannerOrder, boolean canOptimizeForNonNullColumn) throws IOException; StoreFileReader getReader(); void closeReader(boolean evictOnClose) throws IOException; void markCompactedAway(); void deleteReader() throws IOException; Notice that these methods are still available in HStoreFile. And the return value of getFirstKey and getLastKey are changed from Cell to Optional<Cell> to better indicate that they may not be available.