RFR: 8304701: Request with timeout aborts later in-flight request on HTTP/1.1 cxn [v4]

[Conor Cleary]

> **Problem**
> When using HTTP/1.1 with HttpClient, it was observed that requests configured with timeouts at build time fail with a HttpTimeoutException when they are redirected to a separate URI by a server (status code 3xx on first response). What should happen is that the second request response (so after receiving a 3xx code) clears restarts the timer intially set. However, when `responseTimerEvent` is registered for the first time, it is not unregistered and cleared before starting a second timer.
> 
> **Solution**
> This fix addresses the issue by calling `cancelTimer()` in `MultiExchange.java` whenever the `newRequest` reference is set to a non-null value after calling `responseFilters(response)` on the initial response received. This occurs in the case where a status code 3xx is received in the initial response. When `cancelTimer()` is called, it now unreferences `responseTimerEvent` after cancellation operations take place.
> 
> While the fix for the issue was relatively straight forward, the regression test is less so. I would point to to the comment located in `RedirectTimeoutTest:L119` for an explanation of the testing method.

Conor Cleary has updated the pull request incrementally with one additional commit since the last revision:

  8304701: Added adjustTimeout to make us of timeout factor

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16689/files
  - new: https://git.openjdk.org/jdk/pull/16689/files/0a456bfb..5321b898

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16689&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16689&range=02-03

  Stats: 6 lines in 1 file changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/16689.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16689/head:pull/16689

PR: https://git.openjdk.org/jdk/pull/16689