RFR: 8357919: Arena::allocate returns segments with address zero if the segment length is zero after JDK-8345687

[Per Minborg]

After https://bugs.openjdk.org/browse/JDK-8345687 was integrated, zero-length segments always have an address of zero. This may cause problems in certain native methods that can receive segments and/or buffers derived from segments.

This PR also guards for overflow for extremely large allocation requests.

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Commit messages:
 - Fix zero-length allocation

Changes: https://git.openjdk.org/jdk/pull/25485/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25485&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357919
  Stats: 28 lines in 2 files changed: 28 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25485.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25485/head:pull/25485

PR: https://git.openjdk.org/jdk/pull/25485