RFR: 8323999: KeyAgreement cannot be initiated again after a failed initialization [v2]

[Matthew Donovan]

> This PR updates KeyAgreement to re-initialize the `serviceIterator` field when chooseProvider() is called and serviceIterator.hasNext() returns false. This can happen if KeyAgreement object has been initialized with an invalid key and then initialized with a valid key. (See accompanying test.)

Matthew Donovan has updated the pull request incrementally with one additional commit since the last revision:

  fixed whitespace and @test block

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28004/files
  - new: https://git.openjdk.org/jdk/pull/28004/files/d6556fab..2a5ff125

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28004&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28004&range=00-01

  Stats: 4 lines in 1 file changed: 1 ins; 1 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28004.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28004/head:pull/28004

PR: https://git.openjdk.org/jdk/pull/28004