RFR: 8189441: Define algorithm names for keys derived from KeyAgreement

[Weijun Wang]

Allow `Generic` as an algorithm in the `KeyAgreement::generateSecret(alg)` method.

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Commit messages:
 - the fix

Changes: https://git.openjdk.org/jdk/pull/22650/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22650&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8189441
  Stats: 110 lines in 9 files changed: 90 ins; 4 del; 16 mod
  Patch: https://git.openjdk.org/jdk/pull/22650.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22650/head:pull/22650

PR: https://git.openjdk.org/jdk/pull/22650