RFR: 8278757: [s390] Implement AES Counter Mode Intrinsic [v7]

[Lutz Schmidt]

> Please review (and approve, if possible) this pull request.
> 
> This is a s390-only enhancement. It introduces the implementation of an AES-CTR intrinsic, making use of the specific s390 instruction for AES counter-mode encryption.
> 
> Testing: SAP does no longer maintain a full build and test environment for s390. Testing is therefore limited to running some test suites (SPECjbb*, SPECjvm*) manually. But: identical code is contained in SAP's commercial product and thoroughly tested in that context. No issues were uncovered.
> 
> @backwaterred Could you please conduct some "official" testing for this PR? 
> 
> Thank you all!
> 
> Note: some performance figures can be found in the JBS ticket.

Lutz Schmidt has updated the pull request incrementally with one additional commit since the last revision:

  8278757: honor review comments part 2 - resolve TODOs

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8142/files
  - new: https://git.openjdk.java.net/jdk/pull/8142/files/a99a6fbe..9bed793b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8142&range=06
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8142&range=05-06

  Stats: 51 lines in 3 files changed: 37 ins; 2 del; 12 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8142.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8142/head:pull/8142

PR: https://git.openjdk.java.net/jdk/pull/8142