RFR 8130459(M): Add additional validation after heap creation

[sangheon.kim]

Hi all,

Please review this change of adding additional validation on 
command-line flag checking framework.

Recently we introduced Command-line flag checking framework (JDK-8059557 
<https://bugs.openjdk.java.net/browse/JDK-8059557>, JEP 245: Validate 
JVM Command-Line Flag Arguments ) for ranges and constraints.
And most cases this works great.
Unfortunately there are some flags which can be checked after heap 
creation and these flags are hard to be checked under current framework.
In this regard, I suggest to have an additional constraint checking.

This suggestion adds one more constraint checking stage after memory 
initialization.
And if we need more validations we can extend it.

There are 2 big changes.

1. Flag declaration.
'constraint(FUNC)' -> 'constraint(FUNC,TYPE)'
This webrev has 3 types, Anytime, AfterParse and AfterMemoryInit.
- Anytime: current constraint functions which don't use 
CommandLineFlags::finishedInitializing().
- AfterParse: constraint functions which use 
CommandLineFlags::finishedInitializing().
- AfterMemoryInit: I added only YoungPLABSize as an example.
   * All GC related flags will be covered by JDK-8078555 
<https://bugs.openjdk.java.net/browse/JDK-8078555>: GC: implement ranges 
(optionally constraints) for those flags that have them missing.

2. Previous constraint functions have to use 
'CommandLineFlags::finishedInitializing()' if the flag needs to be 
checked after Argument::parse().
However, with this suggestion there's no need to call the function. 
Instead framework will decide when the constraint function is needed to 
be called.
And previously constraint functions are called twice while this change 
will call each constraint function only one time.

CR: https://bugs.openjdk.java.net/browse/JDK-8130459
webrev: http://cr.openjdk.java.net/~sangheki/8130459/webrev.00/
Testing: JPRT, UTE(vm.quick-pcl) and tests at test/runtime/CommandLine.

Thanks,
Sangheon