Radix Sort in C#: .NET 10, long exponent, negatives and a copy-per-call benchmark - #2372

Moves csharp-algorithms/RadixSort to net10.0 with BenchmarkDotNet 0.15.8 and MSTest 4.5.2. RadixSort() now returns an empty array right away and uses a long exponent so an array holding int.MaxValue takes 10 passes instead of 12, CountingSort() drops the redundant zero-fill loop, and the new RadixSortWithNegatives() shifts by the smallest value with a checked subtraction. The benchmark moves into RadixSortBenchmarks, copies its input before every call so no call sorts already sorted data, and compares against Array.Sort() on random, sorted and imbalanced input. Program.cs passes args to BenchmarkRunner. Tests use (expected, actual) order and gain six cases, 10 in total.