[lworld] RFR: 8367551: Cherrypick ImageReader refactoring PR (JDK-8360037)

[duke]

On Fri, 12 Sep 2025 14:12:00 GMT, David Beaumont <duke at openjdk.org> wrote:

> Cherry pick ImageReader work to unblock progress on preview mode in Valhalla.

@david-beaumont 
Your change (at version cd9a73386203401e93b2836c7fb2b212fa5dfa4e) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/valhalla/pull/1581#issuecomment-3285650230