RFR: 8254965: Remove unused Matcher::_ruleName and make ruleName non-product

[Claes Redestad]

- Matcher::_ruleName is unused - remove
- ruleName, defined via ad, is only used by a non-product routine. #ifdef it accordingly

This reduces the JVM size (-63Kb on linux-x64, or about 0.25%)

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Commit messages:
 - Matcher::_ruleName unused and ruleName only used by non-product code

Changes: https://git.openjdk.java.net/jdk/pull/722/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=722&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254965
  Stats: 5 lines in 3 files changed: 2 ins; 3 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/722.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/722/head:pull/722

PR: https://git.openjdk.java.net/jdk/pull/722