Prototype a fully functional `unsigned int128` type as a Valhalla value class.
--------- - [x] I confirm that I make this contribution in accordance with the [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). ------------- Commit messages: - 8383809: [type-classes] Prototype UInt128 Changes: https://git.openjdk.org/valhalla/pull/2420/files Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2420&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8383809 Stats: 2011 lines in 5 files changed: 2010 ins; 0 del; 1 mod Patch: https://git.openjdk.org/valhalla/pull/2420.diff Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2420/head:pull/2420 PR: https://git.openjdk.org/valhalla/pull/2420
