RFR: JDK-8318006: remove unused net related coding

[Matthias Baesken]

[JDK-8253119](https://bugs.openjdk.org/browse/JDK-8253119) removed the old socket implementation code but it did leave some unused code behind, it would be good to remove these unused functions.

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Commit messages:
 - JDK-8318006

Changes: https://git.openjdk.org/jdk/pull/16164/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16164&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318006
  Stats: 141 lines in 3 files changed: 0 ins; 141 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16164.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16164/head:pull/16164

PR: https://git.openjdk.org/jdk/pull/16164