RFR: 8350616: Skip ValidateHazardPtrsClosure in non-debug builds

[David Holmes]

Simple cleanup to skip debug code in a non-debug build. This removes some overhead when working with very large numbers of threads. Basic perf testing starting a new thread when 20000 already exist:

Before: 532377 ns
After:  361178 ns

which is 32% improvement.

Testing:
  - tiers 1-3 sanity

Thanks

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Commit messages:
 - 8350616: Skip ValidateHazardPtrsClosure in non-debug builds

Changes: https://git.openjdk.org/jdk/pull/23762/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23762&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350616
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23762.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23762/head:pull/23762

PR: https://git.openjdk.org/jdk/pull/23762