RFR: 8209137: Add ability to bind to specific local address to HTTP client [v18]

[Jaikiran Pai]

> This change proposes to implement the enhancement noted in https://bugs.openjdk.java.net/browse/JDK-8209137.
> 
> The change introduces a new API to allow applications to build a `java.net.http.HTTPClient` configured with a specific local address that will be used while creating `Socket`(s) for connections.

Jaikiran Pai has updated the pull request incrementally with two additional commits since the last revision:

 - Daniel's review suggestion - add a test to verify the behaviour of the localAddress() default method implementation on HttpClient.Builder
 - Daniel's review suggestion - remove reference to "Internet Protocol" in javadoc

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6690/files
  - new: https://git.openjdk.java.net/jdk/pull/6690/files/d4a19dea..3a6f2b6b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6690&range=17
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6690&range=16-17

  Stats: 74 lines in 2 files changed: 70 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6690.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6690/head:pull/6690

PR: https://git.openjdk.java.net/jdk/pull/6690