feat: Add more unit tests in Core to increase coverage

[Kryptos-FR]

PR Details

Improve the code coverage of Stride.Core.AssemblyProcessor, Stride.Core.Yaml, Stride.Core and Stride.Core.IO.

Related PR

#2967

Details

A few bugs were identified during testing and fixed.

MultiValueSortedList<TKey, TValue>

Bug 1: Binary search in Add() method failed to maintain sorted order

• Cause: Loop condition while (greater - lower > 1) prevented proper sorting for lists with 0-1 elements
• Impact: Items were not inserted in sorted order (e.g., adding 5,2,8,1 resulted in [5,2,8,1] instead of [1,2,5,8])
• Fix: Replaced with standard binary search algorithm using while (lower < upper) pattern

Bug 2: Indexer returned incomplete results for duplicate keys

• Cause: BinarySearch returns an arbitrary matching index, not necessarily the first occurrence
• Impact: When multiple values shared the same key, only a subset was returned (e.g., 1-2 values instead of all 3)
• Fix: Added backward scan to find first occurrence before returning values: while (index > 0 && keys[index - 1].Equals(key)) index--;

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.