Use CoreCLRs GetCustomAttributes implementation in native AOT

[MichalStrehovsky]

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[MichalStrehovsky]

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[Copilot]

🟡 Changes recommended

The NativeAOT RuntimeParameterInfo changes can regress pseudo-attribute behavior when metadata is unavailable, and there’s also a fixable allocation regression in an empty-result hot path.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR routes NativeAOT reflection attribute queries/instantiation through the shared CoreCLR-style RuntimeCustomAttribute implementation (in RuntimeCustomAttributeData.cs), removing the older NativeAOT-specific RuntimeCustomAttribute/instantiator logic and updating NativeAOT reflection surface area to call the new path.

Changes:

• Add/expand NativeAOT implementations in RuntimeCustomAttributeData.cs for constructor resolution, argument decoding, and instantiation from NativeFormat metadata.
• Update NativeAOT Type/MemberInfo implementations to validate attributeType and call RuntimeCustomAttribute.* for IsDefined/GetCustomAttributes.
• Remove the old NativeAOT-only custom attribute implementation files and their csproj entries; add helper APIs to find constructors by metadata identity.

File summaries

File	Description
src/coreclr/System.Private.CoreLib/src/System/Reflection/RuntimeCustomAttributeData.cs	Adds NativeAOT custom attribute ctor resolution/instantiation helpers and wires NativeAOT RuntimeCustomAttribute to use them.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/RuntimeType.NativeAot.cs	Redirects IsDefined/GetCustomAttributes* to RuntimeCustomAttribute with CoreCLR-like argument validation.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/RuntimeMethodInfo.cs	Uses RuntimeCustomAttribute for CA queries with UnderlyingSystemType validation.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/RuntimeCustomAttribute.NativeAot.cs	Removes the previous NativeAOT custom attribute implementation.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/TypeInfos/RuntimeTypeInfo.GetMember.cs	Adds GetConstructorWithSameMetadataDefinitionAs(...) used by NativeAOT ctor resolution.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/TypeInfos/RuntimeTypeInfo.cs	Removes CA query forwarding methods now handled elsewhere.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/PropertyInfos/RuntimePropertyInfo.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/ParameterInfos/RuntimeParameterInfo.cs	Updates CA query entrypoints and adds metadata-reader guards (currently problematic).
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/Modules/RuntimeModule.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/MethodInfos/RuntimePlainConstructorInfo.cs	Adds a helper overload for metadata-identity comparison.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/MethodInfos/RuntimeConstructorInfo.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/FieldInfos/RuntimeFieldInfo.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/EventInfos/RuntimeEventInfo.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/Assemblies/RuntimeAssemblyInfo.cs	Updates CA query entrypoints to RuntimeCustomAttribute and validates attributeType.
src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj	Removes compilation of deleted NativeAOT CA files.
src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Reflection/Extensions/NonPortable/CustomAttributeInstantiator.cs	Removes the previous NativeAOT CustomAttributeData→Attribute instantiation helper.

Review details

Suppressed comments (1)

src/coreclr/nativeaot/System.Private.CoreLib/src/System/Reflection/Runtime/ParameterInfos/RuntimeParameterInfo.cs:66

• RuntimeParameterInfo.IsDefined returns false when GetMetadataReader() is null, which can incorrectly hide pseudo custom attributes (e.g., In/Out/Optional) that don’t require metadata. RuntimeCustomAttribute.IsDefined already accounts for pseudo attributes and treats a null reader as “no metadata attributes”.

        public sealed override bool IsDefined(Type attributeType, bool inherit)
        {
            ArgumentNullException.ThrowIfNull(attributeType);

            if (GetMetadataReader() is null)
                return false;

            if (attributeType.UnderlyingSystemType is not RuntimeType attributeRuntimeType)
                throw new ArgumentException(SR.Arg_MustBeType, nameof(attributeType));

            return RuntimeCustomAttribute.IsDefined(this, attributeRuntimeType);

• Files reviewed: 16/16 changed files
• Comments generated: 2
• Review effort level: Lite