RFR: JDK-8304557: java/util/concurrent/CompletableFuture/CompletableFutureOrTimeoutExceptionallyTest.java times out [v2]

[Viktor Klang]

> Improves the stability of the memory leak test for CompletableFuture timeout cancellation by both reducing the count by 50% (which should still be above threshold to trigger given the ample margin set initially) as well as extending the default timeout of the test run.

Viktor Klang has updated the pull request incrementally with one additional commit since the last revision:

  Changing the test to monitor the internals instead of trying to provoke an OOME

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13116/files
  - new: https://git.openjdk.org/jdk/pull/13116/files/a135c253..4a5dd8c8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13116&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13116&range=00-01

  Stats: 32 lines in 1 file changed: 17 ins; 0 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/13116.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13116/head:pull/13116

PR: https://git.openjdk.org/jdk/pull/13116