perf: Reduce allocations and eliminate boxing across ProgressBar, SparkChart, Picker, SegmentedControl, and EffectsView

[PaulAndersonS]

Root Cause of the Issue

Multiple controls have unnecessary heap allocations and CPU overhead in hot paths (rendering, layout, touch events) due to:

• LINQ methods (OrderBy().ToList(), Distinct().ToList(), First(), Last()) creating intermediate collections
• IEnumerable<Enum> return types causing boxing of value-type enums
• string.ToString() comparisons instead of direct enum equality checks
• OfType<T>().FirstOrDefault() and Cast<T>() creating unnecessary enumerator wrappers

Description of Change

5 targeted performance improvements:

1. ProgressBar Utility.UpdateGradientStopCollection — Replace OrderBy().ToList() with in-place List.Sort() and cache First()/Last() as direct [0]/[Count-1] indexer access. Eliminates LINQ allocation + 4 redundant enumerations.

2. SparkAreaChart OnDraw — Cache segment[0], segment[Count-1], and Count before the inner loop. Eliminates repeated First()/Last() calls in the per-frame rendering hot path.

3. DatePickerHelper & TimePickerHelper — Replace Distinct().ToList() with HashSet<int>-based RemoveAll(). Deduplicates in-place without allocating a new list.

4. SegmentedControl SegmentLayout — Replace Children.OfType<T>().FirstOrDefault() and Children.Cast<T>() with direct foreach+type-check loops with early exit. Avoids enumerator allocations.

5. EffectsView Utils.cs — Change GetAllItems() / GetAllAutoResetEffectsItems() return types from IEnumerable<Enum> to IEnumerable<SfEffects> / IEnumerable<AutoResetEffects>. Eliminates boxing, removes .ToString() comparisons (replaced with direct enum equality), and removes .Select(v => (T)v) cast wrappers at call sites.

Issues Fixed

N/A — Proactive performance improvement (no user-reported issue)

Unit Tests Added

• ProgressBarUtilityUnitTests — 5 tests verifying sort order, boundary insertion at start/end, and no-op when range is covered
• EffectsViewUtilsUnitTests — 6 tests verifying flag decomposition for None, single flags, and combined flags for both SfEffects and AutoResetEffects

Screenshots

N/A — No visual changes