RFR: 8297878: KEM: Implementation [v5]

[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:

  fine tune spec

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/13256/files
  - new: https://git.openjdk.org/jdk/pull/13256/files/6455a521..39c3a202

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=03-04

  Stats: 8 lines in 2 files changed: 4 ins; 0 del; 4 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