RFR: 8325513: Export method for Cipher [v6]

[Weijun Wang]

> Add `Cipher::exportKey` 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 18 additional commits since the last revision:

 - Merge branch 'master' into 8325513
 - new since, more UOE cases
 - Merge branch 'master' into 8325513
 - exportData
 - plural
 - Merge branch 'master' into 8325513
 - small update
 - Merge branch 'master' into 8325513
 - change new method to non final
 - rename
 - ... and 8 more: https://git.openjdk.org/jdk/compare/09946dbd...9f9cd651

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18409/files
  - new: https://git.openjdk.org/jdk/pull/18409/files/cd02570c..9f9cd651

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18409&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18409&range=04-05

  Stats: 616694 lines in 9446 files changed: 413711 ins; 137944 del; 65039 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