RFR: 8350279: HttpClient: Add a new HttpResponse method to identify connections [v12]

[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 one additional commit since the last revision:

  Add `@implNote` to state that the built-in is always non-empty

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24154/files
  - new: https://git.openjdk.org/jdk/pull/24154/files/db61a015..a1bb8cf0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24154&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24154&range=10-11

  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 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