RFR: JDK-8299475: Enhance SocketException by cause where it is missing in net and nio area [v6]

[Matthias Baesken]

> We have a couple of places where a SocketException is thrown but the cause is omitted. It would be beneficial for example in error analysis not to throw away the cause (causing exception) but to add it to the created SocketException.

Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:

  Introduce asSocketException in nio

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11813/files
  - new: https://git.openjdk.org/jdk/pull/11813/files/62916a71..655cf6ff

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11813&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11813&range=04-05

  Stats: 20 lines in 1 file changed: 14 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/11813.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11813/head:pull/11813

PR: https://git.openjdk.org/jdk/pull/11813