RFR: 8282900: runtime/stringtable/StringTableCleaningTest.java verify unavailable at this moment

[Robbin Ehn]

Hi, please consider:

verify() is called by GC in safepoint so it should use the corresponding scanning method.
verify_and_compare_entries() can wait for until there is no resize.

This makes these methods always succeed, passes t1-t6.

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Commit messages:
 - Use non-failable CHT scan methods.

Changes: https://git.openjdk.org/jdk/pull/10527/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10527&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282900
  Stats: 8 lines in 1 file changed: 1 ins; 5 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/10527.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10527/head:pull/10527

PR: https://git.openjdk.org/jdk/pull/10527