RFR: 8297878: Implementing Key Encapsulation Mechanism API

[Weijun Wang]

The KEM API and DHKEM impl. Note that this PR uses new methods in https://github.com/openjdk/jdk/pull/13250.

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Commit messages:
 - the fix

Changes: https://git.openjdk.org/jdk/pull/13256/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297878
  Stats: 2222 lines in 9 files changed: 2214 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/13256.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13256/head:pull/13256

PR: https://git.openjdk.org/jdk/pull/13256