[FEATURE] Support more storage index types for Neo4j/Postgres

[badmonster0]

We only support primary key index and vector index now. We may add support for more index types, e.g. text index, range index.

Implementation wise, currently it's tedious to build the logic to manage each index type, e.g. we need to compare with pervious states and diff against it, and often needs a "DROP IF NOT EXISTS" before creating (for updating existing indexes). #295 is an example.