RFR: 8318096: Introduce AsymmetricKey interface with a getParams method [v4]

[Weijun Wang]

> Create a parent interface `AsymmetricKey` for `PublicKey` and `PrivateKey` and add a `getParams` method there. This makes it available to all current and future public and private keys.
> 
> No test. Might add one.

Weijun Wang has updated the pull request incrementally with one additional commit since the last revision:

  no longer sealed

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16222/files
  - new: https://git.openjdk.org/jdk/pull/16222/files/8017cc4d..096b95a1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16222&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16222&range=02-03

  Stats: 4 lines in 3 files changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16222.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16222/head:pull/16222

PR: https://git.openjdk.org/jdk/pull/16222