RFR: 8371475: HttpClient: Implement CUBIC congestion controller [v3]

[Daniel Jeliński]

>> CUBIC is a standard TCP congestion control algorithm that uses a cubic function instead of a linear congestion window increase function to improve scalability and stability over fast and long-distance networks. CUBIC has been adopted as the default TCP congestion control algorithm by the Linux, Windows, and Apple stacks.
> 
> This PR adds a new congestion controller algorithm. It reuses a large part of the QuicRenoCongestionController, which was refactored to two classes - QuicBaseCongestionController, containing the shared code, and QuicRenoCongestionController, containing only the code that is unique to Reno.
> 
> CUBIC is now the default congestion controller. Reno can still be selected by setting the system property `jdk.httpclient.quic.congestionController` to `reno`.
> 
> A new test was added to exercise the new congestion controller. Existing tests continue to pass.

Daniel Jeliński has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 24 commits:

 - Update test comments
 - Convert CubicTest to JUnit
 - Merge declaration and assignment
 - More aggressive target growth
 - Merge remote-tracking branch 'origin/master' into quic-cubic
 - Make classes final
 - Rename system property to internal
 - Add a system property to select congestion controller
 - Implement fast convergence
 - Add comments
 - ... and 14 more: https://git.openjdk.org/jdk/compare/1f1f7bb4...195b0f89

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Changes: https://git.openjdk.org/jdk/pull/28195/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28195&range=02
  Stats: 970 lines in 6 files changed: 709 ins; 254 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/28195.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28195/head:pull/28195

PR: https://git.openjdk.org/jdk/pull/28195