RFR: 8325513: Export method for Cipher [v4]

[Weijun Wang]

> Add `Cipher::export` API.

Weijun Wang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 14 additional commits since the last revision:

 - plural
 - Merge branch 'master' into 8325513
 - small update
 - Merge branch 'master' into 8325513
 - change new method to non final
 - rename
 - Merge branch 'master' into 8325513
 - make test work
 - Add test
 - Wording
 - ... and 4 more: https://git.openjdk.org/jdk/compare/aa7dccb2...11701dce

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18409/files
  - new: https://git.openjdk.org/jdk/pull/18409/files/bbd97a30..11701dce

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18409&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18409&range=02-03

  Stats: 1380673 lines in 17253 files changed: 849599 ins; 410568 del; 120506 mod
  Patch: https://git.openjdk.org/jdk/pull/18409.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18409/head:pull/18409

PR: https://git.openjdk.org/jdk/pull/18409