RFR: 8208693: HttpClient: Extend the request timeout's scope to cover the response body [v14]

[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 one additional commit since the last revision:

  Exclude disallowed timer cancellations

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27469/files
  - new: https://git.openjdk.org/jdk/pull/27469/files/802ce9de..0487a137

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27469&range=13
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27469&range=12-13

  Stats: 61 lines in 5 files changed: 40 ins; 6 del; 15 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