[logging] Log RFC3339 timestamp for better granularity
[logging] Log RFC3339 timestamp for better granularity

Currently, the timestamp in structured logs is just the day and time, in
seconds.  This gives us better granularity by using a well known time
format that will let us order all of the logs.

Closes: #5563

aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra