RFR: 8349910: Implement JEP 517: HTTP/3 for the HTTP Client API [v14]

[Daniel Fuchs]

> Hi,
> 
> Please find here a PR for the implementation of [JEP 517: HTTP/3 for the HTTP Client API](https://openjdk.org/jeps/517).
> 
> The CSR can be viewed at [JDK-8350588: Implement JEP 517: HTTP/3 for the HTTP Client API](https://bugs.openjdk.org/browse/JDK-8350588)
> 
> This JEP proposes to enhance the HttpClient implementation to support HTTP/3.
> It adds a non-exposed / non-exported internal implementation of the QUIC protocol based on DatagramChannel and the SunJSSE SSLContext provider.

Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 628 commits:

 - merge latest changes from master branch
 - http3: minor code cleanup
 - http3: HeadersLowerCaseTest.java should close the clients it creates
 - http3: add missing copyright in Http3ConnectionAccess and make the class final
 - http3: improved test coverage for ImmutableSSLSession
 - http3: make sure that abandonned HTTP/2 connections are closed
 - http3: CustomRequestPublisher.java test should take into account server config
 - Add QUIC support to SunX509 key manager, update copyrights
 - Move getAlgorithmConstraints to X509KeyManagerCertChecking, update to match surrounding code
 - Mark H3ErrorHndlingTest as intermittent
 - ... and 618 more: https://git.openjdk.org/jdk/compare/ae0dac43...719f471d

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Changes: https://git.openjdk.org/jdk/pull/24751/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24751&range=13
  Stats: 105864 lines in 475 files changed: 103026 ins; 1335 del; 1503 mod
  Patch: https://git.openjdk.org/jdk/pull/24751.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24751/head:pull/24751

PR: https://git.openjdk.org/jdk/pull/24751