RFR: 8320449: ECDHKeyAgreement should validate parameters before using them

[John Jiang]

ECDHKeyAgreement should validate the parameters before assigning them to the fields.

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Commit messages:
 - 8320449: ECDHKeyAgreement should validate parameters before using them

Changes: https://git.openjdk.org/jdk/pull/17373/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17373&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320449
  Stats: 125 lines in 2 files changed: 108 ins; 9 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/17373.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17373/head:pull/17373

PR: https://git.openjdk.org/jdk/pull/17373