RFR: 8259074: regex benchmarks and tests [v3]

[Martin Buchholz]

> 8259074: regex benchmarks and tests

Martin Buchholz has updated the pull request incrementally with two additional commits since the last revision:

 - refactor correctness checking as suggested by @shipilev
 - prune @Param values as suggested by Claes

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1940/files
  - new: https://git.openjdk.java.net/jdk/pull/1940/files/abb6c672..5faba5e7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1940&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1940&range=01-02

  Stats: 89 lines in 3 files changed: 44 ins; 25 del; 20 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1940.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1940/head:pull/1940

PR: https://git.openjdk.java.net/jdk/pull/1940