RFR: 8297878: KEM: Implementation [v11]

[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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 11 additional commits since the last revision:

 - Merge branch 'master' into 8297878
 - no more pk/sk, AIOOBE to IOOBE
 - small spec change
 - some constants, no local reverse
 - fine tuning spec
 - move Encapsulator before Decapsulator
 - fine tune spec
 - let implementor validate arguments, null key throws IKE
 - spec changes
 - spec change, getAlgorithm
 - ... and 1 more: https://git.openjdk.org/jdk/compare/13457d46...8ba16065

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/13256/files
  - new: https://git.openjdk.org/jdk/pull/13256/files/7ada6f0b..8ba16065

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=10
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13256&range=09-10

  Stats: 311246 lines in 3091 files changed: 261349 ins; 31771 del; 18126 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