perf: Chart control performance improvements

[PaulAndersonS]

Root Cause of the Issue

Multiple performance bottlenecks in the Chart control's hot paths causing unnecessary allocations and repeated enumeration during render cycles.

Description of Change

This PR implements 10 performance improvements targeting allocation reduction and LINQ elimination in frequently-called Chart control code paths:

1. Hoist .ToList() outside loop in GetTotalWidth() — CartesianChartArea.cs: .Values.ToList()[i] was creating a new list on every iteration.

2. Replace GetType().Name.Contains() with is pattern matching — CartesianChartArea.cs: String-based type checks in CalculateStackingValues() inner loop replaced with compile-time type checks (is StackingColumn100Series or StackingLine100Series or StackingArea100Series).

3. Cache indexed X values in GetXValues() — CartesianSeries.cs: LINQ .ToList() was creating a new list on every call. Now caches the computed index list and invalidates on data source changes.

4. Replace .Where().Sum() with single foreach loop — CartesianChartArea.cs: GetYValue() static method no longer double-enumerates the collection.

5. Remove .Where().ToList() in ResetVisibleSeries() — StackingSeriesBase.cs: Direct iteration with inline predicate instead of allocating a filtered list.

6. Remove .Where().ToList() in ResetSBSSegments() — CartesianChartArea.cs: Direct iteration instead of allocating a filtered list just to set flags.

7. Replace .Any() with manual loop in UpdateStackingSeries() — CartesianChartArea.cs: Eliminates LINQ delegate allocation with early-exit foreach loop.

8. Eliminate Cast<object>().ToList() in ResetDataPoint() — ChartSeriesPartial.cs: Uses IEnumerable.GetEnumerator().MoveNext() to check for data existence without allocating a full list copy.

9. Pre-compute coordinates in zoom/pan selection rendering — ChartZoomPanView.cs: Cache computed x/y coordinates outside if/else branches to avoid redundant ternary evaluations per axis; reuse axisRect local for actualArrangeRect computation.

10. Replace nested LINQ .FirstOrDefault().Any() with foreach loops — CartesianChartArea.cs: SBS grouping lookup now uses nested foreach with early break instead of LINQ with reflection.

Issues Fixed

N/A — Performance improvement (no functional changes)

Screenshots

N/A — Internal implementation optimization only