RFR: 8201179: Regression due loading java.nio.charset.StandardCharsets during bootstrap

[Claes Redestad]

Hi,

JDK-8200310 cleaned up java.nio.charset.StandardCharsets to not use 
Charset.forName, but also removed the optimization to have 
unconditionally loaded charsets set up static INSTANCE constants, which 
means that many systems the java.nio.charset.StandardCharsets will be 
initialized in System.initPhase1.

This should be avoided since at this point the VM is just booting up and 
any code executed delays initialization of JIT etc.

Webrev: http://cr.openjdk.java.net/~redestad/8201179/open.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8201179

This patch makes all the constants in j.n.c.StandardCharsets use new 
INSTANCE fields of each respective Charset and adds some comments as to 
why they exist.

I also think we should avoid depending on j.n.c.StandardCharsets within 
java.base as to not accidentally execute more code in initPhase1 than 
absolutely necessary, so I've changed uses in core packages (java.lang, 
java.util, java.zip...) to use the internal alternative.

Thanks!

/Claes