API diff between .NET 9 Preview 3 and .NET 9 Preview 4

[carlossanlop]

Repo area owners:

• ASP.NET - @dotnet/aspnet-api-review
• WinForms - @merriemcgaw @dreddy-work @JeremyKuhne
• WPF - @singhashish-wpf and @pchaurasia14
• Libraries - @artl93 @jeffschwMSFT @jeffhandley @karelz @ericstj @stephentoub

Libraries area owners:

• @dotnet/area-system-codedom
• @dotnet/area-system-formats-asn1
• @dotnet/area-system-io
• System.IO.Pipes @dotnet/aspnet-api-review
• @dotnet/area-system-numerics
• @dotnet/area-system-reflection-emit
• @dotnet/area-system-runtime-compilerservices
• System.Runtime.InteropServices @dotnet/interop-contrib
• @dotnet/area-system-runtime-intrinsics
• @dotnet/area-system-security
• @dotnet/area-system-text-encoding
• @dotnet/area-system-text-json
• System.Threading @kouvel @mangod9
• @dotnet/area-system-threading-channels
• @dotnet/area-system-threading-tasks

Known api-diff tool issues:

If yo usee any of these, please provide a GitHub suggestion in this PR to correct it:

• The AsmDiff tool sometimes skips adding { or {} arcade#10981([AsmDiff] For attributes, move the +/- diff symbol to the attribute instead of the affected API arcade#13814)
• RequiresPreviewAttribute not getting auto added arcade#14498
• Changes to protected internal visibility should stop showing. AsmDiff: Do not show APIs with protected internal visibility arcade#14579
• The AsmDiff tool shows APIs with decorating attribute changes as removed and re-added, instead of showing only the API. Please ignore this, it might be confusing but technically it's not incorrect: [arcade#13814]

[adamsitnik]

System.IO* LGTM!

[eiriktsarpalis]

STJ changes LGTM.