RFR: 8368966: Remove spurious VMStructs friends

[Stefan Karlsson]

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).

Marked as reviewed by stefank (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/27583#pullrequestreview-3293095646