RFR: 8327991: Improve HttpClient documentation with regard to reclaiming resources [v5]

[Daniel Fuchs]

> Please find here a doc-only change that tries to better document how resources allocated by the HttpClient are reclaimed.
> The `@implNote` in the HttpClient class level API documentation is extended to document what happens if you don't explicitly close the HttpClient. The note is refactored to introduce the notion of streaming or publishing bodies. BodySubscribers and BodyHandlers now have links that link back to the HttpClient API note, as well as identifying methods that return publishing or streaming body implementations.

Daniel Fuchs has updated the pull request incrementally with one additional commit since the last revision:

  Copyright years

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18270/files
  - new: https://git.openjdk.org/jdk/pull/18270/files/4f830897..3bffdea1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18270&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18270&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18270.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18270/head:pull/18270

PR: https://git.openjdk.org/jdk/pull/18270