Review/sponsor request: 6850361 Avoid 2-step lookup in sun.nio.cs charset providers

[Ulf Zibis]

Martin, Sherman, Dalibor,

do you like to review and/or sponsor my CR ?

This fix would additionally speed-up the lookup of charsets and save some memory.
The footprint of the code is again little smaller than before.

See:
https://bugs.openjdk.java.net/show_bug.cgi?id=100095

Thanks,

Ulf