RFR (M) 8026977: NPG: Remove ConstantPool::lock

[Coleen Phillimore]

Summary: Write klass and resolved_references constant pool fields lock free.

The constant pool values that can change were already read lock free, 
through the cpSlot type (lsb set for Symbol vs. Klass) for 
JVM_CONSTANT_{Unresolved}Class.   With Permgen elimination, the other 
values that can change were moved to the resolved_references array, 
which is initialized to null.  Non-null is the resolved value.  With a 
couple uses of CAS, we can eliminate the need for the constant pool lock 
for the constant pool changes.   Error handling also changes the tag but 
saving the resolution exception was done under the 
SystemDictionary_lock, so only the tag change needs a CAS.

The only remaining use for the constant pool lock is updating the 
cpCache for invokedynamic.  There are 4 fields that need to be 
consistent.   These now use the metaspace lock associated with the class 
loader that owns the constant pool, which is only held briefly.   I ran 
some performance tests written by Sergey Kuksenko which show no regression.

Other testing - ran refworkload on linux x64 with no significant 
results.  Passed JPRT (runThese), vm.quick.testlist, jck8 tests, hotspot 
jtreg tests and jdk java/lang/invoke jtreg tests.

open webrev at http://cr.openjdk.java.net/~coleenp/8026977/
bug link https://bugs.openjdk.java.net/browse/JDK-8026977

Thanks,
Coleen