RFR: 8365820: Apply certificate scope constraints to algorithms in "signature_algorithms" extension when "signature_algorithms_cert" extension is not being sent

[Artur Barashev]

[JDK-8349583](https://bugs.openjdk.org/browse/JDK-8349583) implementation assumes that OpenJDK client always sends "signature_algorithms_cert" extension together with "signature_algorithms" extension. But we didn't account for `jdk.tls.client.disableExtensions` and `jdk.tls.server.disableExtensions` system properties which can disable producing "signature_algorithms_cert" extension. This is an issue similar to [JDK-8355779](https://bugs.openjdk.org/browse/JDK-8355779) but on the extension producing side.

Per TLSv1.3 RFC:

>  If no "signature_algorithms_cert" extension is
>    present, then the "signature_algorithms" extension also applies to
>    signatures appearing in certificates.

Also making a few cosmetic changes to the existing code.

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Commit messages:
 - 8365820: Apply certificate scope constraints to algorithms in "signature_algorithms" extension when "signature_algorithms_cert" extension is not being sent

Changes: https://git.openjdk.org/jdk/pull/26887/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26887&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365820
  Stats: 264 lines in 6 files changed: 229 ins; 25 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/26887.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26887/head:pull/26887

PR: https://git.openjdk.org/jdk/pull/26887