Call NewDataBlockIterator with correct arguments in DB::Get (#4913)

Summary:
The pointer `get_context` was passed as the value for the boolean argument `index_key_is_full`. Luckily the pointer was always non-null so evaluated to true which is the correct value for the boolean argument. But we were missing out on batch updates to stats since we were not passing anything for the `GetContext*` argument and it defaults to `nullptr`.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4913

Differential Revision: D13791449

Pulled By: ajkr

fbshipit-source-id: dbe40bf406c64d34cb5298604145d18b9e0ca9be

table/block_based_table_reader.cc

@@ -2518,7 +2518,8 @@ Status BlockBasedTable::Get(const ReadOptions& read_options, const Slice& key,
         DataBlockIter biter;
         NewDataBlockIterator<DataBlockIter>(
             rep_, read_options, iiter->value(), &biter, false,
-            true /* key_includes_seq */, get_context);
+            true /* key_includes_seq */, true /* index_key_is_full */,
+            get_context);
 
         if (read_options.read_tier == kBlockCacheTier &&
             biter.status().IsIncomplete()) {