[Forward Compatibility] Add support for timestamps in Logs chain metadata

[AhmedSoliman]

Log chain should carry unique timestamps of segments via HLC clock.

[muhamadazmy]

Would love to have some more context over this issue:

• Why is this needed?
• What does this timestamp represent? is it creation timestamp of the segment? What is that going to be used for in the future?
• The HLC UniqueTimestamp is not serder. Is this by design ? We might need to add this if we going to use HLC in metadata or other objects. Conversion to MillisSinceEpoch drops the logical part of the timestamp. Do we really need HLC timestamp in the logs, or MillisSinceEpoch is enough? and why HLC is needed?