RFR: 8348195: More u2 conversion warnings after JDK-8347147

[Aleksey Shipilev]

After [JDK-8347147](https://bugs.openjdk.org/browse/JDK-8347147), SonarCloud reports a few risky conversions from int to u2. It would be good to cover them with either checked_cast or changing the underlying type.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jdk/pull/23217/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23217&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348195
  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/23217.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23217/head:pull/23217

PR: https://git.openjdk.org/jdk/pull/23217