Add JSON benchmarks for missing-property and case-insensitive

[steveharter]

Adds new benchmarks to track changes made in dotnet/runtime#35848

Verifies ~2x perf improvement on the missing-property and case-insensitive scenarios.

Before changes from the runtime PR linked above:

|                     Method |     Mean |     Error |    StdDev |   Median |      Min |      Max |  Gen 0 | Gen 1 | Gen 2 | Allocated |
|--------------------------- |---------:|----------:|----------:|---------:|---------:|---------:|-------:|------:|------:|----------:|
|        DeserializeBaseline | 1.209 us | 0.0139 us | 0.0130 us | 1.207 us | 1.186 us | 1.231 us | 0.0676 |     - |     - |     448 B |
|         DeserializeMissing | 1.593 us | 0.0161 us | 0.0150 us | 1.595 us | 1.557 us | 1.622 us | 0.0386 |     - |     - |     264 B |
|    DeserializeCaseMatching | 1.304 us | 0.0120 us | 0.0112 us | 1.301 us | 1.289 us | 1.329 us | 0.1169 |     - |     - |     752 B |
| DeserializeCaseNotMatching | 2.369 us | 0.0240 us | 0.0224 us | 2.371 us | 2.333 us | 2.411 us | 0.1426 |     - |     - |     928 B |

After:

|                     Method |       Mean |    Error |   StdDev |     Median |        Min |        Max |  Gen 0 | Gen 1 | Gen 2 | Allocated |
|--------------------------- |-----------:|---------:|---------:|-----------:|-----------:|-----------:|-------:|------:|------:|----------:|
|        DeserializeBaseline | 1,228.1 ns | 12.32 ns | 11.53 ns | 1,226.9 ns | 1,210.2 ns | 1,246.1 ns | 0.0685 |     - |     - |     448 B |
|         DeserializeMissing |   841.5 ns |  6.32 ns |  5.60 ns |   840.0 ns |   831.2 ns |   851.4 ns | 0.0134 |     - |     - |      88 B |
|    DeserializeCaseMatching | 1,224.4 ns | 12.83 ns | 12.00 ns | 1,224.7 ns | 1,209.8 ns | 1,246.2 ns | 0.0676 |     - |     - |     448 B |
| DeserializeCaseNotMatching | 1,234.0 ns |  9.58 ns |  8.49 ns | 1,233.8 ns | 1,223.1 ns | 1,249.1 ns | 0.0688 |     - |     - |     448 B |

[billwert]

Can you rename this? The current name took going to your original issue for me to understand.

Suggested change

	public T DeserializeMissing() => JsonSerializer.Deserialize<T>(_serializedCamelCased, _optionsBaseline);
	public T DeserializeWithMissingProperties() => JsonSerializer.Deserialize<T>(_serializedCamelCased, _optionsBaseline);

May also be worth a comment to make it clear that the properties will be "missing" because we're not using the case insensitive option.

[steveharter]

Hmm one issue with names is that the results comparer truncates at 80 chars, so I've been trying to keep names small otherwise it may not be possible to distinguish between tests in the output.

However I didn't do a good job at that. It looks like System.Text.Json.Serialization.Tests.ReadMissingAndCaseInsensitive<Location>. is already at 77 characters leaving only 3 characters which currently is not even enough to distinguish between the 4 tests I added.

We could fix that issue with the results comparer, or I could simplify the class name and remove "DeserializeWith" but that still doesn't leave enough room to add "Properties".

[billwert]

We should fix that in results comparer. @adamsitnik I assume this was a "nice output" choice and not something technical?

Our actual reporting backend does does not truncate these names (@DrewScoggins to correct me). I'm in favor of descriptive names so we should do what we need to in order to make that possible.

[steveharter]

Made some renames and added comments.

[DrewScoggins]

Yes, we don't truncate.

[billwert]

One change I'd like and then LGTM.

[billwert]

Thanks @steveharter! LGTM. We'll sort out the comparison tool separately.