Improve performance with CharacterOptionExtensions

[FlaggAC]

Improves performance with CharacterOptionExtensions. There is some overhead with calling GetAttributeOfType, so we are pre-caching these results.

Moves CharacterOptionExtensions from ACE.Entity to ACE.Server, as ACE.Entity's .NET Standard doesn't support FrozenDictionary or Enum.GetValues.

I could rewrite this in a way that is compatible with .NET Standard, but it seemed more appropriate for the class to be in ACE.Server anyway so I moved it for now.

[Mag-nus]

CharacterOptionExtensions should either remain in CharacterOptions.cs, or, if it is to be a separate file, it should be in the same folder as CharacterOptions.cs

Also, standard ACE using format is System on top, ACE below, separated by a space, ie:

using System;
using System.Collections.Frozen;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;

using ACE.Entity;
using ACE.Entity.Enum;

[gmriggs]

where did CharacterOptionExtensions sit in the profile of the entire server?

before/after benchmarks for these changes?

[FlaggAC]

For the stress test with 190 connected clients sending nothing but non-rate-limited cg messages the method was about 2% of the entire server and 80% of the handling of the command (Superluminal screenshot attached). I'll get some BenchmarkDotNet measurements and fix the PR for .NET standard so the class won't need to be moved.

[FlaggAC]

Benchmarks (NetStandard_New will be the one used after the PR is fixed)

// * Summary *

BenchmarkDotNet v0.13.12, Windows 11 (10.0.22631.3880/23H2/2023Update/SunValley3)
Intel Core i9-10850K CPU 3.60GHz, 1 CPU, 20 logical and 10 physical cores
.NET SDK 8.0.303
  [Host]     : .NET 8.0.7 (8.0.724.31311), X64 RyuJIT AVX2
  DefaultJob : .NET 8.0.7 (8.0.724.31311), X64 RyuJIT AVX2

| Method                                        | Mean       | Error      | StdDev     | Gen0   | Allocated |
|---------------------------------------------- |-----------:|-----------:|-----------:|-------:|----------:|
| GetCharacterOptions1Attribute_NetStandard_Old | 861.713 ns | 13.2714 ns | 11.0822 ns | 0.0238 |     256 B |
| GetCharacterOptions1Attribute_NetStandard_New |   2.674 ns |  0.0818 ns |  0.0725 ns |      - |         - |
| GetCharacterOptions1Attribute_FrozenDict      |   4.395 ns |  0.0125 ns |  0.0110 ns |      - |         - |
| GetCharacterOptions2Attribute_NetStandard_Old | 317.798 ns |  5.8058 ns |  5.4308 ns | 0.0095 |     104 B |
| GetCharacterOptions2Attribute_NetStandard_New |   2.242 ns |  0.0097 ns |  0.0081 ns |      - |         - |
| GetCharacterOptions2Attribute_FrozenDict      |   1.993 ns |  0.0069 ns |  0.0057 ns |      - |         - |

// * Legends *
  Mean      : Arithmetic mean of all measurements
  Error     : Half of 99.9% confidence interval
  StdDev    : Standard deviation of all measurements
  Gen0      : GC Generation 0 collects per 1000 operations
  Allocated : Allocated memory per single operation (managed only, inclusive, 1KB = 1024B)
  1 ns      : 1 Nanosecond (0.000000001 sec)