RFR: 8327652: S390x: Implements SLP support [v8]

[Sidraya Jayagond]

> This PR Adds SIMD support on s390x.

Sidraya Jayagond has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains nine additional commits since the last revision:

 - Merge branch 'openjdk:master' into Vector_support_s390x
 - PopCountVI supported by z14 onwards.
 - Fix cosmetic review comments
 - Address code cleanup review comments
 - Use Op_VecX instead of Op_RegF
   
   Signed-off-by: Sidraya <sidraya.jayagond at ibm.com>
 - Add proper comments and cosmetic changes.
 - Address review comments
 - Remove extra spcaes
 - Implements SIMD support on s390x

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/18162/files
  - new: https://git.openjdk.org/jdk/pull/18162/files/042c3966..20a12fcf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18162&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18162&range=06-07

  Stats: 744880 lines in 9749 files changed: 244305 ins; 134355 del; 366220 mod
  Patch: https://git.openjdk.org/jdk/pull/18162.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18162/head:pull/18162

PR: https://git.openjdk.org/jdk/pull/18162