RFR (M) Close alignment gaps in InstanceKlass

[coleen.phillimore at oracle.com]

Summary: moved fields around and some constant fields into ConstantPool

This is a simple change except that I moved some constant fields from 
InstanceKlass into the constant pool so they can be shared read-only in 
the CDS archive.  There are associated repercussions in SA and JVMCI, so 
please look at these changes.  Also moved similarly sized fields 
together in the class so there's less likelihood of introducing gaps in 
future InstanceKlass changes.

InstanceKlass is reduced from 544 to 520 bytes in a simple Hello World 
class.

open webrev at http://cr.openjdk.java.net/~coleenp/2020/8238048.01/webrev
bug link https://bugs.openjdk.java.net/browse/JDK-8238048

Tested with tier1-6.

Thanks,
Coleen