8066291: Return unmodifiable set of zone IDs to optimize ZoneIdPrinterParser
Summary: Cache the available zones to speed up parsing
Reviewed-by: rriggs, scolebourne

8134373: use collections convenience factories in the JDK
Reviewed-by: scolebourne, prappo, dfuchs, redestad, smarks
Contributed-by: jbluettduncan@gmail.com

8141652: Rename methods Objects.nonNullElse* to requireNonNullElse*
Summary: And some usages of replacing expr != null ? expr : otherexpr
Reviewed-by: jrose, chegar

8054834: Modular Source Code
Reviewed-by: alanb, chegar, ihse, mduigou
Contributed-by: alan.bateman@oracle.com, alex.buckley@oracle.com, chris.hegarty@oracle.com, erik.joelsson@oracle.com, jonathan.gibbons@oracle.com, karen.kinnear@oracle.com, magnus.ihse.bursie@oracle.com, mandy.chung@oracle.com, mark.reinhold@oracle.com, paul.sandoz@oracle.com