RFR: 8313249: Fix -Wconversion warnings in verifier code

Thu Jul 27 15:57:57 UTC 2023

See bugid for comments.  Most of the verifier code deals with ints, so the u2 and other parameters weren't really needed and can be promoted to int. Mostly types are changed, but a few checked_cast<>s are added.
Tested with tier1-4, sanity Oracle platforms.

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Commit messages:
 - Use some checked_casts even though I know these are < u2.
 - verifier.cpp no warnings

Changes: https://git.openjdk.org/jdk/pull/15056/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15056&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313249
  Stats: 151 lines in 7 files changed: 12 ins; 1 del; 138 mod
  Patch: https://git.openjdk.org/jdk/pull/15056.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15056/head:pull/15056

PR: https://git.openjdk.org/jdk/pull/15056