RFR: 8342188: Update tests to use stronger key parameters and certificates [v3]

[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 incrementally with one additional commit since the last revision:

  DHKeyAgreement2.java refactor

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21563/files
  - new: https://git.openjdk.org/jdk/pull/21563/files/6ce89cbf..7d321b36

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21563&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21563&range=01-02

  Stats: 8 lines in 1 file changed: 2 ins; 0 del; 6 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