RFR: 8376308: java/net/httpclient/CancelRequestTest.java fails intermittently with "Expected CancellationException not received" [v3]

[Daniel Fuchs]

> When using async mode, and if the "wrong" test/client thread gets suspended at the wrong time there's a small time window in which the server might be able to send its reply before the request is cancelled.
> This can be avoided by having the server handler wait on a semaphore until the cancellation exception has been propagated to the caller on the client side.

Daniel Fuchs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Merge branch 'master' into CancelRequestTest-Sem-8376308
 - Review feedback: IOExceptions are not unexpected
 - Review feedback
 - Copyright year + unused imports
 - 8376308: java/net/httpclient/CancelRequestTest.java fails intermittently with "Expected CancellationException not received"

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/29415/files
  - new: https://git.openjdk.org/jdk/pull/29415/files/4fa0b27a..effad463

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29415&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29415&range=01-02

  Stats: 8607 lines in 279 files changed: 5101 ins; 2120 del; 1386 mod
  Patch: https://git.openjdk.org/jdk/pull/29415.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29415/head:pull/29415

PR: https://git.openjdk.org/jdk/pull/29415