feat(cost-model): introduce MemoExt trait for property info

[xx01cyx]

To compute the cost for an expression, we need information about the schema & attribute ref (including attribute correlations). In the current optd, this is done by calling the optimizer core's methods. We were against this approach in previous discussions because we thought this makes the core and the cost model coupled too much -- we thereby eliminated the optimizer parameter and intended to get all these information from the storage/ORM.

However, there is a performance drawback of getting everything from ORM: the core should have all the information (schema & attribute ref) we need in memory -- it would be more efficient for them to be passed in by the core than querying the underlying external database. This also aligns more with the way the cascades optimizer works: building the memo table in a bottom-up approach and remembering everything.

Therefore, to avoid getting everything from ORM and still use one general interface for all types of node, we would need the core to implement a trait provided by the cost model, and the cost model will call the corresponding methods to get the information, i.e. MemoExt in this PR. This allows the core to remain ignorant of what the cost model needs for computing the cost.

[xx01cyx]

Not sure whether it's good to use Arc here.

[skyzh]

This looks fine, otherwise you'll need to add the memo type as part of the cost model impl's generic type parameters.