RFR: 8345176: Add tests to verify java.net.Socket constructors close the socket on failure [v3]

[Volkan Yazıcı]

> [8343791](https://bugs.openjdk.org/browse/JDK-8343791) (addressed by #22160) stresses that `Socket::connect()` failures should be handled such that the resultant state of the `Socket` and its underlying `SocketImpl` should match. In a similar fashion, `Socket::new` (which is using `bind()` and `connect()` under the hood) failures should not leave behind an open `SocketImpl` either. This change set, addressing [8345176](https://bugs.openjdk.org/browse/JDK-8345176), adds `CtorFailTest` verifying this behavior.

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

  Add `MockSocketImpl#toString()` to aid test output visuals

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22439/files
  - new: https://git.openjdk.org/jdk/pull/22439/files/5e492b7b..cf86230d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22439&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22439&range=01-02

  Stats: 15 lines in 1 file changed: 15 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/22439.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22439/head:pull/22439

PR: https://git.openjdk.org/jdk/pull/22439