RFR: 8357808: Add a command line option for specifying a counter in TestRandomFloatingDecimal

[Raffaello Giulietti]

Add a `-Dcount=N` command line option to specify the number of random samples per test (default is 10'000).

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Commit messages:
 - 8357808: Add a command line option for specifying a counter in TestRandomFloatingDecimal

Changes: https://git.openjdk.org/jdk/pull/25460/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25460&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357808
  Stats: 25 lines in 1 file changed: 18 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/25460.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25460/head:pull/25460

PR: https://git.openjdk.org/jdk/pull/25460