RFR: 8349759: Fix CertificateBuilder and SimpleOCSPServer test utilities to support PQC algorithms

[Jamil Nimeh]

This fix makes some minor changes to the internals of the `CertificateBuilder` and `SimpleOCSPServer` test classes.  They would break when ML-DSA was selected as key and signing algorithms.  Also RSASSA-PSS works better now with these changes.  I've also taken this opportunity to do some cleanup on CertificateBuilder and added a method which uses a default signing algorithm based on the key, so the `build()` method no longer needs to provide that algorithm (though one can if they wish for things like RSA signatures if they want a different message digest in the signature).

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Commit messages:
 - 8349759: Fix CertificateBuilder and SimpleOCSPServer test utilities to support PQC algorithms

Changes: https://git.openjdk.org/jdk/pull/23566/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23566&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349759
  Stats: 316 lines in 3 files changed: 269 ins; 13 del; 34 mod
  Patch: https://git.openjdk.org/jdk/pull/23566.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23566/head:pull/23566

PR: https://git.openjdk.org/jdk/pull/23566