RFR: 8297878: KEM: Implementation [v4]

[Weijun Wang]

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

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  let implementor validate arguments, null key throws IKE

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13256/files
  - new: https://git.openjdk.org/jdk/pull/13256/files/b398b03e..6455a521

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=02-03

  Stats: 252 lines in 5 files changed: 51 ins; 180 del; 21 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