RFR: 8281236: (D)TLS key exchange named groups

[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)

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Commit messages:
 - 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=00
  Issue: https://bugs.openjdk.org/browse/JDK-8281236
  Stats: 907 lines in 17 files changed: 657 ins; 200 del; 50 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