Remove some unnecessary EventSource suppressions

[agocke]

Due to the DynamicallyAccessedMembersAttribute on the EventSource type, all members that have DAM/RUC on them produce warnings that need to be suppressed. In NAOT it also causes extra metadata to be preserved.

By moving these members into a nested type, it excludes them from reflection visibility and means we don't have to have suppressions.

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[agocke]

This diff looks messier than it is -- I just moved the two functions inside a nested class and removed the UnconditionalSuppressMessage attributes.

[Copilot]

Pull request overview

Refactors EventSource manifest/attribute reflection helpers into a private nested type to avoid trim-analysis suppressions triggered by EventSource’s [DynamicallyAccessedMembers] annotation (and reduce preserved metadata for NativeAOT).

Changes:

• Route GetGuid, GetName, manifest generation, and descriptor initialization through a new EventSourceHelpers nested type.
• Move CreateManifestAndDescriptors and GetCustomAttributeHelper into the nested helper to remove prior suppressions on those members.

[noahfalk]

Looks good to me. The big diff appears to be caused by the method order in the new nested type not matching exactly the original method order.

[agocke]

/ba-g issue is #125245