Encoding Feature and ULabel uids

[sunnyosun]

Currently, we are not encoding uids of Feature and ULabel, which then cause FeatureSet between different instances to have different uid (hash of the feature uids) even though they contain the same features.
This is a broader discussion about how to make uid immutable and name mutable, and also track the identity of record. For bionty records, this can be done via hashing ontology_id instead of name.