[3.0] Issue 1779: Add DB2zOS support for UNICODE Timestamps

[dazey3]

for #1779

For non-IBM JDKs, against DB2 zOS, the existing test org.eclipse.persistence.jpa.test.version.TestVersioning.testTemporalVersionField1() fails:

<error message="java.nio.charset.UnsupportedCharsetException: Cp1027" type="javax.persistence.RollbackException">javax.persistence.RollbackException: java.nio.charset.UnsupportedCharsetException: Cp1027
	at org.eclipse.persistence.internal.jpa.transaction.EntityTransactionImpl.commit(EntityTransactionImpl.java:159)
	at org.eclipse.persistence.jpa.test.version.TestVersioning.testTemporalVersionField1(TestVersioning.java:62)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at org.eclipse.persistence.jpa.test.framework.EmfRunner.run(EmfRunner.java:40)
Caused by: java.nio.charset.UnsupportedCharsetException: Cp1027
	at java.base/java.nio.charset.Charset.forName(Charset.java:529)
	at com.ibm.db2.jcc.am.x.&lt;init&gt;(x.java:20)
	at com.ibm.db2.jcc.am.w.a(w.java:12)
	at com.ibm.db2.jcc.am.Agent.getByteToCharConverter(Agent.java:497)
	at com.ibm.db2.jcc.t4.a8.a(a8.java:2438)
	at com.ibm.db2.jcc.t4.ab.a(ab.java:4350)
	at com.ibm.db2.jcc.t4.ab.a(ab.java:2777)
	at com.ibm.db2.jcc.t4.ab.a(ab.java:2698)
	at com.ibm.db2.jcc.t4.ab.q(ab.java:1546)
	at com.ibm.db2.jcc.t4.ab.l(ab.java:735)
	at com.ibm.db2.jcc.t4.ab.d(ab.java:111)
	at com.ibm.db2.jcc.t4.p.c(p.java:44)
	at com.ibm.db2.jcc.t4.av.j(av.java:162)
	at com.ibm.db2.jcc.am.k3.an(k3.java:2249)
	at com.ibm.db2.jcc.am.k4.a(k4.java:4638)
	at com.ibm.db2.jcc.am.k4.b(k4.java:4154)
	at com.ibm.db2.jcc.am.k4.bd(k4.java:774)
	at com.ibm.db2.jcc.am.k4.executeQuery(k4.java:739)
	at org.eclipse.persistence.internal.databaseaccess.DatabaseAccessor.executeSelect(DatabaseAccessor.java:1018)

Signed-off-by: William Dazey wadazey@us.ibm.com

[rfelcman]

LGTM (except copyright year in the tests)