RFR: 8365858: FilteredJavaFieldStream is unnecessary

[Coleen Phillimore]

On Thu, 11 Sep 2025 08:35:05 GMT, Paul Hübner <phubner at openjdk.org> wrote:

> Hi all,
> 
> `FilteredJavaFieldStream` purely exists to hide the field `constantPoolOop` in `jdk.internal.reflect.ConstantPool`. This PR:
> 1) refactors `constantPoolOop` to be a hidden VM injected field `vmholder` (name to be consistent with other similar cases),
> 2) removes `FilteredJavaFieldStream` entirely, and
> 3) updates code previously relying on `FilteredJavaFieldStream` to use `JavaFieldStream` instead.
> 
> Testing: Oracle tiers 1-3.

ConstantPool in the JVM metadata used to be called constantPoolOop, so I think that's what it's looking to not find.

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PR Comment: https://git.openjdk.org/jdk/pull/27209#issuecomment-3292895168