[jdk21u-dev] RFR: 8310906: Fix -Wconversion warnings in runtime, oops and some code header files.

[Aleksey Shipilev]

Clean backport to avoid more conversion warnings, and lay the ground for subsequent clean backports.

Additional testing:
 - [ ] Linux x86_64 server fastdebug, `all`
 - [ ] Linux AArch64 server fastdebug, `all`

-------------

Commit messages:
 - Backport 9f46fc28426630399ca39d443403cc3a7be58854

Changes: https://git.openjdk.org/jdk21u-dev/pull/767/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=767&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310906
  Stats: 60 lines in 32 files changed: 8 ins; 0 del; 52 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/767.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/767/head:pull/767

PR: https://git.openjdk.org/jdk21u-dev/pull/767