RFR: 8368966: Remove spurious VMStructs friends

[duke]

On Tue, 30 Sep 2025 16:35:36 GMT, Francesco Andreuzzi <fandreuzzi at openjdk.org> wrote:

> In this PR I propose a small clean up to remove several spurious friends of `VMStructs`. Either I could not find any reference to them in `vmStructs*`, or no private symbols is mentioned.
> 
> Passes tier1 and tier2 (fastdebug).

@fandreuz 
Your change (at version 1f873d0d1e693d0d73772376041cc6171bf13be2) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk/pull/27583#issuecomment-3359787966