RFR: 8365820: Apply certificate scope constraints to algorithms in "signature_algorithms" extension when "signature_algorithms_cert" extension is not being sent [v5]

[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.

Artur Barashev has updated the pull request incrementally with one additional commit since the last revision:

  Add a server-side unit test. Rename existing tests.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26887/files
  - new: https://git.openjdk.org/jdk/pull/26887/files/64fd6927..89867a60

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26887&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26887&range=03-04

  Stats: 604 lines in 5 files changed: 430 ins; 174 del; 0 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