RFR: 4936767: Parameters for MessageDigest

[Weijun Wang]

Add parameters to `MessageDigest` and introduce `SHAKE256-LEN` with an integer parameter.

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Commit messages:
 - new class spec
 - more changes
 - initial change

Changes: https://git.openjdk.org/jdk/pull/16660/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16660&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-4936767
  Stats: 505 lines in 11 files changed: 410 ins; 65 del; 30 mod
  Patch: https://git.openjdk.org/jdk/pull/16660.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16660/head:pull/16660

PR: https://git.openjdk.org/jdk/pull/16660