Feature: introduce the HDFS plugin into RocksDB to support accessing data on HDFS

[empiredan]

Starting from RocksDB 7.0.0, the HDFS support was removed from the main repository and provided instead as a plugin. Since Pegasus currently uses RocksDB 8.5.3, the HDFS plugin needs to be integrated into RocksDB to achieve the following goals:

1. Support maintaining the underlying RocksDB data on HDFS in the Pegasus server, as well as accessing HDFS directly through the RocksDB interfaces.
2. Support generating RocksDB SST files on HDFS via the Java APIs, so that they can be ingested into the Pegasus server using the bulk load tool.

Task list:

• feat(rocksdb): support building RocksDB with the HDFS plugin in the Pegasus server #2362