RFR: 8293064: Remove unused NET_xxx functions

[Darragh Clarke]

No tests were affected so this is purely a removal PR apart from updating copyright headers.
I ran tests for Tier 1,2&3 and everything seems to be passing

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Commit messages:
 - Merge branch 'openjdk:master' into JDK-8293064
 - removed unused methods

Changes: https://git.openjdk.org/jdk/pull/10343/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10343&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293064
  Stats: 582 lines in 8 files changed: 0 ins; 576 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/10343.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10343/head:pull/10343

PR: https://git.openjdk.org/jdk/pull/10343