RFR: 8328168: Epsilon: 'EpsilonHeap::allocate_work' can't allocate an object larger than the uncommitted size

[Guoxiong Li]

Hi all,

When an object size meets the following three conditions, the allocation will fail unexpectedly.

1. `object_size` > `uncommitted_size`
2. `object_size` > `committed_but_unused_size`
3. `object_size` < `unused_size` (`unused_size` equals `uncommitted_size + committed_but_unused_size`)

Please read the newly added test of this patch for the concrete case.

Thanks for taking the time to review.

Best Regrads,
-- Guoxiong

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Depends on: https://git.openjdk.org/jdk/pull/18303

Commit messages:
 - JDK-8328168

Changes: https://git.openjdk.org/jdk/pull/18304/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18304&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328168
  Stats: 48 lines in 2 files changed: 44 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/18304.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18304/head:pull/18304

PR: https://git.openjdk.org/jdk/pull/18304