Using strings for Concat

[SergerGood]

To avoid allocations need to use the method
public static string Concat (string? str0, string? str1, ...
instead of
public static string Concat (object? arg0, object? arg1, ...

BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i5-9300H CPU 2.40GHz, 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=6.0.100-preview.3.21202.5
  [Host]                  : .NET Core 3.1.15 (CoreCLR 4.700.21.21202, CoreFX 4.700.21.21402), X64 RyuJIT
  MediumRun-.NET Core 3.1 : .NET Core 3.1.15 (CoreCLR 4.700.21.21202, CoreFX 4.700.21.21402), X64 RyuJIT

Job=MediumRun-.NET Core 3.1  Runtime=.NET Core 3.1  IterationCount=15  
LaunchCount=2  WarmupCount=10  

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
ConcatOfStrings	39.78 ns	3.453 ns	4.841 ns	0.0076	-	-	32 B
ConcatOfObjects	53.62 ns	4.601 ns	6.450 ns	0.0134	-	-	56 B

    [MemoryDiagnoser]
    [MediumRunJob(RuntimeMoniker.NetCoreApp31)]
    public class Program
    {
        private string _firstStringParam = "1";
        private string _secondStringParam = "2";
        private int _thirdIntParam = 3;
        
        [Benchmark]
        public string ConcatOfStrings()
        {
            return string.Concat(_firstStringParam, _secondStringParam, _thirdIntParam.ToString());
        }
    
        [Benchmark]
        public string ConcatOfObjects()
        {
            return string.Concat(_firstStringParam, _secondStringParam, _thirdIntParam);
        }
    
        private static void Main() => BenchmarkRunner.Run<Program>();
    }