Drop usage of .All on DefaultValueAttribute

[MichalStrehovsky]

This functionality of DefaultValueAttribute constructor is disabled by default and warns if it gets enabled. We shouldn't need to keep things on the type passed to the constructor.

Cc @eerhardt - as you suggested on Teams

[Copilot]

Pull Request Overview

This PR removes the DynamicallyAccessedMemberTypes.All annotation from the DefaultValueAttribute constructor that takes a Type and string parameter. The change is motivated by the fact that this functionality is disabled by default and generates warnings when enabled, making the broad type access requirement unnecessary.

Key changes:

• Removed DynamicallyAccessedMembersAttribute annotation from the constructor parameter
• Added API compatibility suppressions for the breaking change
• Added IL linker warning suppressions to maintain existing developer experience

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/libraries/System.Private.CoreLib/src/System/ComponentModel/DefaultValueAttribute.cs	Removed DynamicallyAccessedMembersAttribute from Type parameter
src/libraries/System.Runtime/ref/System.Runtime.cs	Updated reference assembly to match implementation
src/libraries/apicompat/ApiCompatBaseline.NetCoreAppLatestStable.xml	Added suppressions for API compatibility breaking changes
src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Suppressions.LibraryBuild.xml	Added IL2067 suppression for the constructor

[MichalStrehovsky]

/ba-g helix deadletter

[MichalStrehovsky]

@eerhardt do you think we'd need to mark this one as a breaking change too? it's not clear to me how much this actually worked with the feature switch set to the untrimmable value. presumably one got a hard-to-suppress warning in corelib to begin with.

[eerhardt]

This one doesn't feel critical. But if we are marking a breaking change for others, it feels like we should be consistent.