[jdk18u] RFR: 8284620: CodeBuffer may leak _overflow_arena

[Zhengyu Gu]

A clean and low risk backport to fix a memory leak.

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Commit messages:
 - Backport 4d45c3ebc493bb2c85dab84b97840c8ba093ab1f

Changes: https://git.openjdk.java.net/jdk18u/pull/114/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=114&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284620
  Stats: 7 lines in 1 file changed: 3 ins; 3 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/114.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/114/head:pull/114

PR: https://git.openjdk.java.net/jdk18u/pull/114