RFR: 8375352: java/net/httpclient/ConnectTimeoutWithProxy*.java tests fail on EC2 [v2]

[Volkan Yazici]

> Fix tests using `AbstractConnectTimeout` by replacing the usage of an external host (i.e., `example.com`), which unexpectedly resolves to a real IP address on certain test hosts, with a custom `ServerSocket` bootstrapped by the test.
> 
> The initial PR contains 3 commits:
> 
> 1. b06f2606c88 Replace external domain with a custom `ServerSocket` (i.e., _"the fix"_)
> 2. b9262c7ca01 Remove the need for multiple test files
> 3. d95a335db93 Migrate tests to JUnit
> 
> All commits (i.e., 1, 1+2, and 1+2+3) pass tests.

Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:

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Changes:
  - all: https://git.openjdk.org/jdk/pull/29431/files
  - new: https://git.openjdk.org/jdk/pull/29431/files/466696c1..fc639467

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=29431&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=29431&range=00-01

  Stats: 118 lines in 1 file changed: 72 ins; 1 del; 45 mod
  Patch: https://git.openjdk.org/jdk/pull/29431.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29431/head:pull/29431

PR: https://git.openjdk.org/jdk/pull/29431