RFR: 8333412: [s390x] Add support for branch on count instruction

[Amit Kumar]

Adds support for BCT, BCTG, BCTR instructions.

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Commit messages:
 - BCT, BCTG, BCTR instructions support

Changes: https://git.openjdk.org/jdk/pull/19572/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19572&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333412
  Stats: 28 lines in 2 files changed: 23 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/19572.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19572/head:pull/19572

PR: https://git.openjdk.org/jdk/pull/19572