Cache lookups to IEnumerable<IYamlTypeConverter>

[MattKotsenas]

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Several types accept an IEnumerable<IYamlTypeConverter>, and then repeatedly traverse the list searching for a converter that accepts the type to be serialized. Traversing an IEnumerable with LINQ results in an enumerator (to walk the IEnumerable) and a Func (to filter the enumerable) allocation per visitor per object serialized. In the benchmark setup this results in 12 allocations per object serialized.

To avoid the repeated lookups and allocations, I introduced an internal TypeConverterCache that accepts the collection of type converters and maps the type to convert to the first IYamlTypeConverter that accepts the type (the same as the previous behavior). This eliminates all 12 allocations and has a small CPU time win as well.

To avoid a breaking change, I left the protected IEnumerable<IYamlTypeConverter> and added a private TypeConverterCache on PreProcessingPhaseObjectGraphVisitorSkeleton. If / when we want to remove cruft and can accept breaking changes we can remove this field.

Note that each type that previously was doing list traversal has its own cache. If it's OK to change the constructor signature on these types, we could instead construct a single cache in the builder (e.g. in BuilderSkeleton.BuildTypeConverters) and pass it in. However, I assume the builder is designed for public extension, so I avoided that in this change.

In the provided benchmark, this results in a 15% - 25% reduction in allocations:

Before

// * Summary *

BenchmarkDotNet v0.14.0, Windows 11 (10.0.22635.4010)
Intel Core i9-10940X CPU 3.30GHz, 1 CPU, 28 logical and 14 physical cores
.NET SDK 9.0.100-preview.7.24407.12
  [Host]                       : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX-512F+CD+BW+DQ+VL
  MediumRun-.NET 8.0           : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX-512F+CD+BW+DQ+VL
  MediumRun-.NET Framework 4.7 : .NET Framework 4.8.1 (4.8.9261.0), X64 RyuJIT VectorSize=256

IterationCount=15  LaunchCount=2  WarmupCount=10

| Method     | Job                          | Runtime            | Mean      | Error    | StdDev   | Gen0      | Gen1     | Gen2     | Allocated |
|----------- |----------------------------- |------------------- |----------:|---------:|---------:|----------:|---------:|---------:|----------:|
| Serializer | MediumRun-.NET 8.0           | .NET 8.0           |  49.16 ms | 1.436 ms | 2.105 ms | 2000.0000 | 500.0000 |        - |  24.44 MB |
| Serializer | MediumRun-.NET Framework 4.7 | .NET Framework 4.7 | 109.79 ms | 2.546 ms | 3.569 ms | 7800.0000 | 600.0000 | 200.0000 |     48 MB |

// * Warnings *
MinIterationTime
  SerializationBenchmarks.Serializer: MediumRun-.NET 8.0 -> The minimum observed iteration time is 91.906ms which is very small. It's recommended to increase it to at least 100ms using more operations.

// * Hints *
Outliers
  SerializationBenchmarks.Serializer: MediumRun-.NET 8.0           -> 1 outlier  was  removed (57.76 ms)
  SerializationBenchmarks.Serializer: MediumRun-.NET Framework 4.7 -> 2 outliers were removed (121.75 ms, 123.43 ms)

After

// * Summary *

BenchmarkDotNet v0.14.0, Windows 11 (10.0.22635.4010)
Intel Core i9-10940X CPU 3.30GHz, 1 CPU, 28 logical and 14 physical cores
.NET SDK 9.0.100-preview.7.24407.12
  [Host]                       : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX-512F+CD+BW+DQ+VL
  MediumRun-.NET 8.0           : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX-512F+CD+BW+DQ+VL
  MediumRun-.NET Framework 4.7 : .NET Framework 4.8.1 (4.8.9261.0), X64 RyuJIT VectorSize=256

IterationCount=15  LaunchCount=2  WarmupCount=10

| Method     | Job                          | Runtime            | Mean      | Error    | StdDev   | Gen0      | Gen1     | Gen2     | Allocated |
|----------- |----------------------------- |------------------- |----------:|---------:|---------:|----------:|---------:|---------:|----------:|
| Serializer | MediumRun-.NET 8.0           | .NET 8.0           |  46.67 ms | 1.620 ms | 2.425 ms | 1500.0000 | 500.0000 |        - |  17.95 MB |
| Serializer | MediumRun-.NET Framework 4.7 | .NET Framework 4.7 | 108.68 ms | 3.342 ms | 5.002 ms | 6600.0000 | 600.0000 | 200.0000 |  41.49 MB |

// * Warnings *
MultimodalDistribution
  SerializationBenchmarks.Serializer: MediumRun-.NET 8.0 -> It seems that the distribution can have several modes (mValue = 2.83)
MinIterationTime
  SerializationBenchmarks.Serializer: MediumRun-.NET 8.0 -> The minimum observed iteration time is 85.323ms which is very small. It's recommended to increase it to at least 100ms using more operations.

// * Hints *
Outliers
  SerializationBenchmarks.Serializer: MediumRun-.NET 8.0           -> 1 outlier  was  removed (52.89 ms)
  SerializationBenchmarks.Serializer: MediumRun-.NET Framework 4.7 -> 1 outlier  was  removed (122.13 ms)