RFR: 8343772: Expected IAPE not thrown in KDF.getInstance (TCK) [v2]

[Kevin Driver]

> TCK/spec compliance fix for two `getInstance` methods in KDF - unwrap a wrapped IAPE from an NSAE.

Kevin Driver has updated the pull request incrementally with one additional commit since the last revision:

  review comments and fill empty exception message elsewhere

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21961/files
  - new: https://git.openjdk.org/jdk/pull/21961/files/1961b16e..48b5635f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21961&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21961&range=00-01

  Stats: 7 lines in 2 files changed: 4 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21961.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21961/head:pull/21961

PR: https://git.openjdk.org/jdk/pull/21961