RFR: 8350279: HttpClient: Add a new HttpResponse method to identify connections [v6]

[Volkan Yazici]

> Adds `HttpResponse::connectionLabel` method that provides an identifier for the connection.
> 
> **Implementation note:** The feature is facilitated by `HttpConnection::label`, which should not be confused with `HttpConnection::id`. This distinction is explained in the JavaDoc of both properties.

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

 - Remove timeout from `CountDownLatch::await` calls
 - Replace `@AutoClose` with a corresponding `@AfterEach` method
 - Remove IDE-specific `OptionalGetWithoutIsPresent` warning suppression
 - Improve `HttpConnection::label` JavaDoc
 - Start from 1 while labeling connections

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24154/files
  - new: https://git.openjdk.org/jdk/pull/24154/files/883135d8..5b418fd7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24154&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24154&range=04-05

  Stats: 16 lines in 2 files changed: 6 ins; 4 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/24154.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24154/head:pull/24154

PR: https://git.openjdk.org/jdk/pull/24154