RFR: 8343653: [s390x] Replace load/store sequence with move instruction

[Amit Kumar]

Replaces load+store with mvc/mvghi instruction for in-memory operation. Tier1 test are clean except `ShowRegistersOnAssertTest.java` failure, but it failed on head stream also. I am doing git bisect to figure out what's going with that test.  

Testing: 
- tier1 test with no flag 
- tier1 with -XX:+UseCompactObjectHeaders

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Commit messages:
 - replace load + store with in memory move instruction

Changes: https://git.openjdk.org/jdk/pull/22408/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22408&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8343653
  Stats: 17 lines in 5 files changed: 6 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/22408.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22408/head:pull/22408

PR: https://git.openjdk.org/jdk/pull/22408