RFR: 8342188: Update tests to use stronger key parameters and certificates [v7]

[Fernando Guallini]

> Several tests are identified to use weak key parameters (prime modulus, private/public values) and certs with weak keys. As these tests purpose is not to exercise weak keys, these are updated in this PR to use a modulus with 2048-bit, base 2 and certificates with key size 2048

Fernando Guallini has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains nine commits:

 - Merge branch 'master' into 8342188
 - Address comments
 - minor changes to update SecurityUtils comments and refactoring
 - Merge branch 'master' into 8342188
 - Use hex value for diffieHellmanGroup enum
 - DHKeyAgreement2.java refactor
 - DH group reusable
 - fixed copyright year and not changing DES
 - initial commit

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Changes: https://git.openjdk.org/jdk/pull/21563/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21563&range=06
  Stats: 2728 lines in 15 files changed: 1090 ins; 395 del; 1243 mod
  Patch: https://git.openjdk.org/jdk/pull/21563.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21563/head:pull/21563

PR: https://git.openjdk.org/jdk/pull/21563