RFR: 8297822: De-duplicate code in module jdk.sctp

[Per Minborg]

This PR proposes merging logic and optimising three classes that exist for aix, maces and windows.

Optimisation will reduce byte code. Below is an example for one of the many methods optimised.

Before:

public void implCloseSelectableChannel() throws java.io.IOException;
  Code:
     0: new           #7                  // class java/lang/UnsupportedOperationException
     3: dup
     4: ldc           #11                 // String SCTP not supported on this platform
     6: invokespecial #13                 // Method java/lang/UnsupportedOperationException."<init>":(Ljava/lang/String;)V
     9: athrow


After:

public void implCloseSelectableChannel() throws java.io.IOException;
  Code:
     0: invokestatic  #16                 // Method sun/nio/ch/sctp/UnsupportedUtil.sctpUnsupported:()Ljava/lang/UnsupportedOperationException;
     3: athrow

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

Commit messages:
 - De-duplicate code in module jdk.sctp

Changes: https://git.openjdk.org/jdk/pull/11436/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11436&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8297822
  Stats: 1226 lines in 13 files changed: 389 ins; 825 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/11436.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11436/head:pull/11436

PR: https://git.openjdk.org/jdk/pull/11436