RFR: 8290391: Reduce runtime of java.util package microbenchmarks

[Eric Caspole]

Adds Warmup, Measurement and Fork annotations to reduce the run time from 1 day 16 hours to 8 hours for this set.

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Commit messages:
 - 8290391: Reduce runtime of java.util package microbenchmarks

Changes: https://git.openjdk.org/jdk/pull/9523/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9523&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290391
  Stats: 173 lines in 16 files changed: 71 ins; 85 del; 17 mod
  Patch: https://git.openjdk.org/jdk/pull/9523.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9523/head:pull/9523

PR: https://git.openjdk.org/jdk/pull/9523