Ubuntu 20.04: Upgrade RocksDB

[WadeBarnes]

For the Ubuntu 20.04 version of Plenum, upgrade to RocksDB 5.17, which is the version supported on Ubuntu 20.04; https://packages.ubuntu.com/search?searchon=sourcenames&keywords=rocksdb

Background:

• Plenum is currently dependent on RocksDB 5.8.8.
• When RocksDB 5.17 is used without any code changes several tests hang due to issues encountered by the code under test with the updated version of RocksDB. See #1546 for additional details.
• Therefore updates to the code are required to support RocksDB 5.17
• As an interim solution the RocksDB 5.8.8 package built by the Build 3rd Party Dependencies job (of the GHA Workflow) will be used. Refer to #1546 (comment) for details.

[manolaz]

I will work on that upgrade