RFR: 8309692: Fix -Wconversion warnings in javaClasses

[Coleen Phillimore]

Please review this trivial patch to remove implicit integer conversions in javaClasses.inline.hpp/cpp files.
Tested tier1-4.

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Commit messages:
 - 8309692: Fix -Wconversion warnings in javaClasses

Changes: https://git.openjdk.org/jdk/pull/14397/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14397&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309692
  Stats: 10 lines in 3 files changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/14397.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14397/head:pull/14397

PR: https://git.openjdk.org/jdk/pull/14397