Add maxSamples limit

[PaurushGarg]

This PR implements max_samples limit enforcement to prevent OOM by tracking samples at the operator level.

Changes:

• Added SampleTracker in query/ package with Add(), Remove(), and CheckLimit() methods
• Added MaxSamples field to Engine.Opts (default 0 = unlimited)
• Added ErrMaxSamplesExceeded error for limit violations

Tracking Implementation:

Uses delta-based tracking (similar to peak_samples pattern) in three operators:

• vectorSelector: Tracks StepVector samples across batches
• matrixSelector: Tracks ring buffer samples (sliding window)
• subquery: Tracks ring buffer samples (sliding window)

Operator queries buffer.SampleCount(), compares to previous count, and tracks the delta using Add()/Remove().

[MichaHoffmann]

I think we should not support this at the engine here especially not at a logical level - if anything this needs to be pushed down into storage.

[PaurushGarg]

I think we should not support this at the engine here especially not at a logical level - if anything this needs to be pushed down into storage.

Thanks for the feedback! Updated to track only at storage layer (vectorSelector, matrixSelector) similar to peak_samples - at operator level where samples are decoded. Also added tracking in subquery operator since it accumulates samples in ring buffers.