Support FilterExec with embedded projections in WindowTopN optimization

[SubhamSinghal]

Is your feature request related to a problem or challenge?

Discussion thread

The WindowTopN physical optimizer rule currently skips FilterExec nodes that have an embedded projection (filter.projection().is_some()). This happens when ProjectionPushdown runs before WindowTopN and embeds a projection into the FilterExec.

// Don't handle filters with projections
if filter.projection().is_some() {
    return None;
} 

Describe the solution you'd like

Extend WindowTopN to handle FilterExec with embedded projections. This would require:

1. Extracting the projection mapping from FilterExec
2. Resolving the window column index through the projection (mapping projected column indices back to the original schema)
3. Carrying the projection forward into the replacement plan (either re-wrapping PartitionedTopKExec with a ProjectionExec, or embedding the projection)

Describe alternatives you've considered

No response

Additional context

No response