Support requested features on Postgresql online store

[NhuanTDBK]

Is your feature request related to a problem? Please describe.
As a user, I want to retrieve subset of features on Postgresql online store instead of fetching all features

Describe the solution you'd like
Update online_read method to retrieve subset of features

Additional context
I'm close to creating a pull request for this issue myself.

[felixwang9817]

hey @NhuanTDBK, are you sure that Postgres currently doesn't support retrieving a subset of features?

I took a quick look at #3203 and I noticed that the sqlite online store online_read method also does not make use of requested_features; that is because later on the requested features are correctly subselected in FeatureStore._read_from_online_store here

I would be surprised if this didn't also work for Postgres

[NhuanTDBK]

@felixwang9817 I think it's more efficient when it pushed down predicates to Postgres instead of fetching all features and filter out in the client side (For this case, we want to build the AutoFeatureSelection module to automatically select the best features from thousand of features)

[felixwang9817]

@NhuanTDBK sorry for the slow response here - that makes sense to me, I'll stamp your PR!