RFR: 8316060: test/hotspot/jtreg/runtime/reflect/ReflectOutOfMemoryError.java may fail if heap is huge

[Sergey Bylokhov]

The test tries to generate the OOM by filling the whole heap, unfortunately it may fail if the heap is large than 25G. If the heap is around 15-20G the test is quite slow.

The current patch is kind of modified version of the next [fix](https://github.com/openjdk/jdk/pull/14070/files#r1199632388), but instead of increasing timeout it minimize the amount of memory used by the heap.

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Commit messages:
 - 8316060: test/hotspot/jtreg/runtime/reflect/ReflectOutOfMemoryError.java may fail if heap is huge

Changes: https://git.openjdk.org/jdk/pull/15676/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15676&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316060
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15676.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15676/head:pull/15676

PR: https://git.openjdk.org/jdk/pull/15676