RFR: 8373668: Add override keyword to *Klass classes

[Thomas Schatzl]

On Mon, 15 Dec 2025 10:08:18 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> Using override provides better visibility and compiler support for suspicious virtual methods. It makes it clears when reading a class header file if a new virtual interface is introduced or if it simply overridden.
> 
> Testing
>  * GHA
>  * Running tier1 on Oracle supported platforms

Marked as reviewed by tschatzl (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/28820#pullrequestreview-3577857898