Add JsonNumberHandling(Attribute) & support for (de)serializing numbers from/to string

[layomia]

Fixes #30255.

[Dotnet-GitSync-Bot]

Note regarding the new-api-needs-documentation label:

This serves as a reminder for when your PR is modifying a ref *.cs file and adding/modifying public APIs, to please make sure the API implementation in the src *.cs file is documented with triple slash comments, so the PR reviewers can sign off that change.

[steveharter]

From other pending changes per offline review, LGTM.

[layomia]

Barring benchmark noise, there are no noticeable perf regressions caused by this PR:

dotnet run --base D:\benchmarks\numbers\master --diff D:\benchmarks\numbers\feature --threshold 2%
summary:
better: 4, geomean: 1.039
worse: 4, geomean: 1.034
total diff: 8

Slower	diff/base	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Serialization.Tests.ReadJson.DeserializeFromUtf8Bytes	1.04	81.42	85.00
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes	1.04	15760.37	16318.96
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8By	1.03	318.62	328.68
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes	1.03	120.47	123.72

Faster	base/diff	Base Median (ns)	Diff Median (ns)	Modality
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes	1.04	416.34	400.33
System.Text.Json.Serialization.Tests.WriteJson.Serializ	1.04	462715.53	445168.06
System.Text.Json.Serialization.Tests.WriteJson.SerializeToUtf8Bytes	1.04	808.07	778.40
System.Text.Json.Serialization.Tests.ReadJson.Deseri	1.04	304.35	293.22

feature.zip
master.zip