RFR: 8297878: KEM: Implementation [v7]

[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 tuning spec

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13256/files
  - new: https://git.openjdk.org/jdk/pull/13256/files/fe6d73b3..d1a7f3e8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=05-06

  Stats: 85 lines in 2 files changed: 29 ins; 18 del; 38 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