RFR: 8366457: Add ResourceArea and Arena allocators for the RBTree

[Johan Sjölen]

This PR adds Arena and ResourceArea allocators to the RBTree. The test checks that we can make RBTrees from these allocators and that a basic upsert works.

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Commit messages:
 - Add allocators

Changes: https://git.openjdk.org/jdk/pull/29082/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29082&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366457
  Stats: 50 lines in 2 files changed: 49 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29082.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29082/head:pull/29082

PR: https://git.openjdk.org/jdk/pull/29082