RFR: 8324209: Check implementation of Expect: 100-continue in the java.net.http.HttpClient [v5]

[Darragh Clarke]

> Currently `HttpClient` will timeout if a server doesn't respond to a request which includes `Expect: 100-Continue`
> 
> Section 10.1.1 of [rfc 9110](https://datatracker.ietf.org/doc/html/rfc9110#name-expect) states that
> 
> a client SHOULD NOT wait for an indefinite period before sending the content.
> 
> 
> 
> This PR changes `HttpClient` to wait for a maximum of 5 seconds for a server response, this will be shorter if a timeout is set. If no response is received, the message will be sent regardless. 
> This should bring `HttpClient` in line with how [HttpUrlConnection](https://github.com/DarraghClarke/jdk/blob/61386c199a3b29457c002ad31a23990b7f6f88fd/src/java.base/share/classes/sun/net/www/protocol/http/HttpURLConnection.java#L1305) treats expect continue timeouts.
> 
> This is done using `orTimeout` in the `expectContinue` method , though there is some changes in `streams.java` where it was possible for race conditions to cause timeouts where `CompleteableFuture`s were removed from `response_cfs` prematurely or in some cases not removed at all.
> 
> I've tested this against tiers 1-3 and it appears to be stable.

Darragh Clarke has updated the pull request incrementally with one additional commit since the last revision:

  fixed formatting

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20525/files
  - new: https://git.openjdk.org/jdk/pull/20525/files/65d65a15..8ef19ffc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20525&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20525&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20525.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20525/head:pull/20525

PR: https://git.openjdk.org/jdk/pull/20525