8012326: Deadlock occurs when Charset.availableCharsets() is called by several threads at the same time
Summary: removed the race condition risk from  ExtendedCahrset access code
Reviewed-by: mchung, alanb

Reviewed-by: chegar, ksrini

Summary: Migrated all jis based charsets to new implementation
Reviewed-by: okutsu

Reviewed-by: darcy, weijun