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

Tue Jun 27 12:49:28 UTC 2023

This is another version of PR https://github.com/openjdk/jdk/pull/14659 but I've added a pointer delta function in globalDefinitions.hpp to use for these pointer diff calculations that return int everywhere.  If the name is agreeable, I'll fix the other cases of this like this.  It's better than raw casts.
Tested with tier1-4.

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Commit messages:
 - 8310906: Fix -Wconversion warnings in runtime, oops and some code header files.

Changes: https://git.openjdk.org/jdk/pull/14675/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14675&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310906
  Stats: 59 lines in 31 files changed: 8 ins; 0 del; 51 mod
  Patch: https://git.openjdk.org/jdk/pull/14675.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14675/head:pull/14675

PR: https://git.openjdk.org/jdk/pull/14675