Support multi-level chaining of find_also_related for querying multiple related entities

[cnwzhu]

SeaORM's find_also_related only supports two chained calls and does not allow multiple chained invocations. Is it possible to improve this? Otherwise, it's not feasible to query multiple related entities in a single call.
For example, the following pattern fails to compile or function as expected:

EntityA::find()
    .find_also_related::<EntityB>()
    .find_also_related::<EntityC>() 
    .find_also_related::<EntityD>()
    .find_also_related::<EntityE>()  
    .all(&db)
    .await?;