RFR: 8251216: Implement MD5 intrinsics on AArch64

[Patric Hedlin]

Implementation of MD5 intrinsic support for AArch64.

Contributed by Ludovic Henry (@luhenry).

Speedup measured (in Aurora running Ampere Altra) as follows:

openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:1048576-provider:...29.39%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:2047-provider:.........28.91%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:2048-provider:.........28.81%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:1023-provider:.........28.43%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:1024-provider:.........28.32%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:511-provider:...........27.78%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:512-provider:...........27.62%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:255-provider:...........26.52%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:256-provider:...........26.38%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:127-provider:...........25.41%
openjdk.bench.javax.crypto.full.MessageDigestBench.digest-algorithm:MD5-dataSize:128-provider:...........24.66%

Testing tier1-7.

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Commit messages:
 - 8251216: Implement MD5 intrinsics on AArch64

Changes: https://git.openjdk.java.net/jdk/pull/6628/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6628&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8251216
  Stats: 199 lines in 4 files changed: 193 ins; 1 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6628.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6628/head:pull/6628

PR: https://git.openjdk.java.net/jdk/pull/6628