RFR: 8208693: HttpClient: Extend the request timeout's scope to cover the response body [v10]

[Volkan Yazici]

> Currently `HttpRequest::timeout` only applies until the response headers are received. Extend its scope to also cover the consumption of the response body.
> 
> ### Review guidelines
> 
> 1. Read _"the fix"_ in `MultiExchange`
> 2. Skim through the test server *handler* in `TimeoutResponseTestSupport`
> 3. Review first `TimeoutResponseHeaderTest`, and then `TimeoutResponseBodyTest` (Mind the multiple `@test` blocks!)

Volkan Yazici has updated the pull request incrementally with two additional commits since the last revision:

 - Clarify WebSocket behaviour and test it
 - Verify no lingering response timers

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27469/files
  - new: https://git.openjdk.org/jdk/pull/27469/files/480349b6..c5eae908

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27469&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27469&range=08-09

  Stats: 207 lines in 7 files changed: 195 ins; 2 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/27469.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27469/head:pull/27469

PR: https://git.openjdk.org/jdk/pull/27469