frontend: support concrete stream type rather than using BoxStream

[ZENOTME]

Is your feature request related to a problem? Please describe.

as discuss in #5556
We use BoxStream to transfer data now. But Boxstream will impact the performance because it's a dynamic bind. Boxstream is Box, it's a dynamic bind. So I guess every time we call 'stream.next()' to get a row, it needs to call by some mechanism like vtable. Hence if there are millions of rows in the result set, we may need to access vtable millions of times.

Describe the solution you'd like

``The solution is to implement the concrete type which implements stream trait, such as:

struct LocalQueryStream {
 ...
}
impl Stream for LocalQueryStream{
  fn poll_next(){
   ...
  }
}

so that we can use the concrete result type instead of BoxStream to prevent dynamic binding.

// original version
struct PgResponse{
  ...
  result: BoxStream<>
}

// new version 
struct PgResponse{
  result: LocalQueryStream
}

Describe alternatives you've considered

No response

Additional context

No response

[Gun9niR]

Should we use enum dispatch for different concrete stream types?

[ZENOTME]

Yes, Because we have different stream: LocalQueryStream and DistributeQueryStream.

[Gun9niR]

I wonder how many generic params you have used in your previous attempt. I imagine they will appear in fn signatures containing QueryResultSet/PgResultSet, and PgResponse's declaration? How many generic params are introduced?