RFR: 8281236: (D)TLS key exchange named groups [v3]

[Xue-Lei Andrew Fan]

> This update is to support key exchange named groups customization for individual (D)TLS connection. Please review the CSR as well:
> CSR: https://bugs.openjdk.org/browse/JDK-8291950
> RFE: https://bugs.openjdk.org/browse/JDK-8281236
> Release-note: https://bugs.openjdk.org/browse/JDK-8291975
> 
> This is an effort similar to [JDK-8280494: "(D)TLS signature schemes"](https://bugs.openjdk.org/browse/JDK-8280494)

Xue-Lei Andrew Fan has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge
 - Merge
 - add test cases
 - 8281236: (D)TLS key exchange algorithms

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

Changes: https://git.openjdk.org/jdk/pull/9776/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9776&range=02
  Stats: 893 lines in 16 files changed: 657 ins; 195 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/9776.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9776/head:pull/9776

PR: https://git.openjdk.org/jdk/pull/9776