Improve reflection utils speed (#377)

[DemoJameson]

here is the benchmark

BenchmarkDotNet=v0.13.1, OS=Windows 10.0.19044.1620 (21H2)
Intel Core i7-4790 CPU 3.60GHz (Haswell), 1 CPU, 8 logical and 4 physical cores
  [Host]   : .NET Framework 4.8 (4.8.4470.0), X64 RyuJIT
  Mono x64 : Mono 6.12.0 (Visual Studio), X64 

Job=Mono x64  Runtime=Mono x64  

|                          Method |        Mean |     Error |     StdDev | Ratio | RatioSD |  Gen 0 | Allocated |
|-------------------------------- |------------:|----------:|-----------:|------:|--------:|-------:|----------:|
|                       DirectSet |   0.6177 ns | 0.0482 ns |  0.0427 ns | 0.002 |    0.00 |      - |         - |
|               FieldInfoSetValue | 297.2050 ns | 5.6635 ns |  5.0206 ns | 1.000 |    0.00 |      - |         - |
|             R2API.SetFieldValue | 227.2970 ns | 4.5213 ns | 10.7454 ns | 0.802 |    0.04 | 0.0391 |         - |
| R2API.SetFieldValueAfterImprove |  90.1908 ns | 1.8251 ns |  3.5163 ns | 0.301 |    0.01 |      - |         - |
|   R2API.DirectInvokeSetDelegate |   2.7984 ns | 0.0871 ns |  0.1548 ns | 0.009 |    0.00 |      - |         - |

[CLAassistant]

All committers have signed the CLA.

[tristanmcpherson]

The low level code here has been great, but seems the interface to it has been less than desired performance wise due to some oversights, and lack of benchmarking. Looks great, thanks for the contribution.