RFR: JDK-8273881: Metaspace: test repeated deallocations

[Thomas Stuefe]

Hi,

this adds a gtest which tests that repeatedly allocate and deallocate from an arena with the same size will not increase the footprint beyond the first allocation (the block should be registered with freeblock management and re-used each time).

Tests:
- manual tests on Ubuntu x64 and x86, with and without guards, and metaspace jtreg tests
- GHAs

Thanks, Thomas

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Commit messages:
 - JDK-8273881-metaspace-test-repeated-deallocs

Changes: https://git.openjdk.java.net/jdk/pull/5546/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5546&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273881
  Stats: 47 lines in 1 file changed: 47 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5546.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5546/head:pull/5546

PR: https://git.openjdk.java.net/jdk/pull/5546